feat(pilot): Phase 2 — What we know (facts) with stable task-lane IDs

Adds the load-bearing structural feature of the FlowPilot migration: a
"What we know" panel that holds confirmed facts for a session, fed by AI
[PROMOTE] markers and engineer-added notes. Facts feed the resolution
note preview (Phase 3) and survive across turns via stable UUIDs assigned
to pending_task_lane items.

Backend:
- FactSynthesisService: create/update/soft-delete facts with atomic
  state_version bumps; LLM-backed synthesize_from_question/check on the
  fact_synthesis (Haiku) action tier per Section 6.6.
- /api/v1/ai-sessions/{id}/facts CRUD + /facts/promote (proposed_text or
  via synthesis). PATCH returns 403 for question/diagnostic_check facts
  (edit the source item instead, Section 7.3).
- unified_chat_service: [PROMOTE] marker parser (JSON-block per Section
  8.1 spec drift note), stable-UUID assignment for pending_task_lane
  questions/actions preserved by exact text/label match across turns.
- ASSISTANT_SYSTEM_PROMPT: documents [PROMOTE] format, when to/not to
  emit, hallucination guardrails, source_ref handling.
- 17 tests covering parser, stable IDs, service validation, CRUD,
  editability rule, both promote modes, 422 null-synthesis path,
  state_version invariant.

Frontend:
- src/components/pilot/sections/{WhatWeKnow,WhatWeKnowItem,AddNoteButton}
  — green-gradient section above Questions, dashed-circle check, inline
  edit/delete gated by the server's editable flag.
- TaskLane gains a whatWeKnowSlot prop (existing assistant/ folder kept
  per the doc's "rename is opportunistic" guidance).
- AssistantChatPage fetches facts on selectChat and refetches after each
  chat send (so [PROMOTE]-synthesized facts appear immediately); auto-
  opens the lane when facts exist.

Verification: end-to-end smoke against the local docker stack confirms
all five endpoints (list/create/patch/delete/promote) plus the 403
editability rule. pytest suite verifies the same with mocked LLM. Live
[PROMOTE] flow remains untested until used in the UI — the marker shape
is covered by parser tests.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/components/assistant/TaskLane.tsx

@@ -38,6 +38,11 @@ interface TaskLaneProps {
   onSubmit: (responses: TaskResponse[]) => void
   onClose: () => void
   loading?: boolean
+  // Slot for the FlowPilot Phase 2 "What we know" section. Rendered above
+  // Questions in the body (per FLOWPILOT-MIGRATION.md Section 3.1). The slot
+  // shape lets the parent own fact-fetching and state-version polling without
+  // pulling that concern into TaskLane.
+  whatWeKnowSlot?: React.ReactNode
 }
 
 // ── Storage helpers ──
@@ -64,7 +69,7 @@ export function clearTaskState(sessionId: string) {
 
 // ── Component ──
 
-export function TaskLane({ questions, actions, sessionId, onSubmit, onClose, loading }: TaskLaneProps) {
+export function TaskLane({ questions, actions, sessionId, onSubmit, onClose, loading, whatWeKnowSlot }: TaskLaneProps) {
   const [tasks, setTasks] = useState<TaskResponse[]>(() => {
     // Try to restore saved state for this session (preserves user's in-progress answers)
     if (sessionId) {
@@ -269,6 +274,9 @@ export function TaskLane({ questions, actions, sessionId, onSubmit, onClose, loa
       {/* Body */}
       <div className="flex-1 overflow-y-auto p-3 space-y-4">
 
+        {/* ── What we know (Phase 2) ── */}
+        {whatWeKnowSlot}
+
         {/* ── Questions Section ── */}
         {questionTasks.length > 0 && (
           <section>

frontend/src/components/pilot/sections/AddNoteButton.tsx

@@ -0,0 +1,87 @@
+/**
+ * "+ Add a note" affordance for the What-we-know section.
+ *
+ * Inline composer that posts a `user_note` fact when the engineer wants to
+ * record something the AI didn't surface (a hunch, an observation, a piece
+ * of customer context). Per FLOWPILOT-MIGRATION.md Section 3.1.
+ */
+import { useState } from 'react'
+import { Plus, Check } from 'lucide-react'
+
+interface AddNoteButtonProps {
+  onAdd: (text: string, summary: string | null) => Promise<void> | void
+}
+
+export function AddNoteButton({ onAdd }: AddNoteButtonProps) {
+  const [open, setOpen] = useState(false)
+  const [text, setText] = useState('')
+  const [summary, setSummary] = useState('')
+  const [busy, setBusy] = useState(false)
+
+  const reset = () => {
+    setText('')
+    setSummary('')
+    setOpen(false)
+  }
+
+  const handleSubmit = async () => {
+    if (!text.trim()) return
+    setBusy(true)
+    try {
+      await onAdd(text.trim(), summary.trim() || null)
+      reset()
+    } finally {
+      setBusy(false)
+    }
+  }
+
+  if (!open) {
+    return (
+      <button
+        onClick={() => setOpen(true)}
+        className="flex items-center gap-1.5 text-[0.75rem] text-muted-foreground hover:text-accent-text transition-colors pl-1 mt-1"
+      >
+        <Plus size={12} />
+        Add a note
+      </button>
+    )
+  }
+
+  return (
+    <div className="rounded-lg border border-default bg-card p-3 mb-2">
+      <textarea
+        autoFocus
+        value={text}
+        onChange={(e) => setText(e.target.value)}
+        placeholder="What did you observe or confirm?"
+        className="w-full rounded-md border border-default bg-input px-2.5 py-1.5 text-[0.8125rem] text-heading placeholder:text-muted-foreground resize-y min-h-[44px] max-h-[140px] focus:outline-none focus:border-accent focus:ring-1 focus:ring-accent/30"
+        rows={2}
+      />
+      <input
+        type="text"
+        value={summary}
+        onChange={(e) => setSummary(e.target.value)}
+        placeholder="Short label (optional)"
+        className="mt-1.5 w-full rounded-md border border-default bg-input px-2.5 py-1 text-[0.75rem] text-heading placeholder:text-muted-foreground focus:outline-none focus:border-accent focus:ring-1 focus:ring-accent/30"
+      />
+      <div className="mt-1.5 flex items-center gap-2">
+        <button
+          onClick={handleSubmit}
+          disabled={busy || !text.trim()}
+          className="flex items-center gap-1 rounded-md bg-accent px-2.5 py-1 text-[0.75rem] font-medium text-white disabled:opacity-40 hover:bg-accent-hover transition-colors"
+        >
+          <Check size={11} /> Add
+        </button>
+        <button
+          onClick={reset}
+          disabled={busy}
+          className="text-[0.75rem] text-muted-foreground hover:text-heading"
+        >
+          Cancel
+        </button>
+      </div>
+    </div>
+  )
+}
+
+export default AddNoteButton

frontend/src/components/pilot/sections/WhatWeKnow.tsx

@@ -0,0 +1,74 @@
+/**
+ * What-we-know section — the load-bearing structural feature of the FlowPilot
+ * task lane (per FLOWPILOT-MIGRATION.md Section 0 architectural claim #2).
+ *
+ * Owns the list of confirmed facts for a session. Facts arrive via three paths:
+ *   1. AI [PROMOTE] markers parsed in unified_chat_service (most common)
+ *   2. Engineer "+ Add a note" (manual user_note)
+ *   3. Engineer-initiated promotion of a question/check (future affordance)
+ *
+ * This component is the parent's contract: it takes a fact list + handlers
+ * and renders the section. Loading/refresh logic lives in the parent
+ * (AssistantChatPage) so it can coordinate with the chat send cycle.
+ */
+import { cn } from '@/lib/utils'
+import type { SessionFact } from '@/api/sessionFacts'
+import { WhatWeKnowItem } from './WhatWeKnowItem'
+import { AddNoteButton } from './AddNoteButton'
+
+interface WhatWeKnowProps {
+  facts: SessionFact[]
+  onAddNote: (text: string, summary: string | null) => Promise<void> | void
+  onUpdateFact: (factId: string, text: string, summary: string | null) => Promise<void> | void
+  onDeleteFact: (factId: string) => Promise<void> | void
+  loading?: boolean
+}
+
+export function WhatWeKnow({
+  facts,
+  onAddNote,
+  onUpdateFact,
+  onDeleteFact,
+  loading,
+}: WhatWeKnowProps) {
+  const count = facts.length
+
+  return (
+    <section
+      className={cn(
+        'rounded-lg p-3 -mx-1 mb-1',
+        // Subtle green-to-transparent gradient distinguishes this section
+        // from the rest of the lane (mockup 01-session-primary.png).
+        'bg-gradient-to-b from-success/[0.05] to-transparent',
+      )}
+    >
+      <div className="sticky top-0 z-10 pb-2" style={{ background: 'var(--color-bg-page)' }}>
+        <div className="flex items-center gap-2 text-[10px] font-semibold uppercase tracking-[1.2px] text-muted-foreground pl-0.5">
+          <span className="w-1.5 h-1.5 rounded-full bg-success" />
+          What we know
+          <span className="text-muted-foreground">·</span>
+          <span className="tabular-nums">{count}</span>
+        </div>
+      </div>
+
+      {count === 0 && !loading && (
+        <div className="text-[0.75rem] text-muted-foreground italic px-1 py-2">
+          Nothing confirmed yet — facts appear here as the engineer answers questions and runs checks.
+        </div>
+      )}
+
+      {facts.map((fact) => (
+        <WhatWeKnowItem
+          key={fact.id}
+          fact={fact}
+          onSave={(text, summary) => onUpdateFact(fact.id, text, summary)}
+          onDelete={() => onDeleteFact(fact.id)}
+        />
+      ))}
+
+      <AddNoteButton onAdd={onAddNote} />
+    </section>
+  )
+}
+
+export default WhatWeKnow

frontend/src/components/pilot/sections/WhatWeKnowItem.tsx

@@ -0,0 +1,152 @@
+/**
+ * Single fact card in the What-we-know section.
+ *
+ * Layout per FLOWPILOT-MIGRATION.md Section 3.1:
+ *   [✓] <fact text>
+ *       <provenance line: 'from question · rules out tenant/license'>
+ *
+ * Editability: the server marks `editable=false` for `question` and
+ * `diagnostic_check` facts (those are edited at the source item, not here).
+ * Manual notes and AI-synthesized facts are editable inline.
+ *
+ * Delete is allowed for all source types — even read-only facts may be
+ * removed when the underlying question or check turned out to be wrong.
+ */
+import { useState } from 'react'
+import { Check, Pencil, Trash2, X } from 'lucide-react'
+import { cn } from '@/lib/utils'
+import type { SessionFact, SessionFactSourceType } from '@/api/sessionFacts'
+
+interface WhatWeKnowItemProps {
+  fact: SessionFact
+  onSave: (text: string, summary: string | null) => Promise<void> | void
+  onDelete: () => Promise<void> | void
+}
+
+const SOURCE_LABEL: Record<SessionFactSourceType, string> = {
+  question: 'from question',
+  diagnostic_check: 'from check',
+  user_note: 'manual note',
+  ai_synthesis: 'synthesized',
+}
+
+export function WhatWeKnowItem({ fact, onSave, onDelete }: WhatWeKnowItemProps) {
+  const [editing, setEditing] = useState(false)
+  const [draftText, setDraftText] = useState(fact.text)
+  const [draftSummary, setDraftSummary] = useState(fact.source_summary ?? '')
+  const [busy, setBusy] = useState(false)
+
+  const handleSave = async () => {
+    if (!draftText.trim()) return
+    setBusy(true)
+    try {
+      await onSave(draftText.trim(), draftSummary.trim() || null)
+      setEditing(false)
+    } finally {
+      setBusy(false)
+    }
+  }
+
+  const handleCancel = () => {
+    setDraftText(fact.text)
+    setDraftSummary(fact.source_summary ?? '')
+    setEditing(false)
+  }
+
+  const handleDelete = async () => {
+    setBusy(true)
+    try {
+      await onDelete()
+    } finally {
+      setBusy(false)
+    }
+  }
+
+  const provenanceLabel = SOURCE_LABEL[fact.source_type]
+
+  if (editing) {
+    return (
+      <div className="rounded-lg border border-default bg-card p-3 mb-2">
+        <textarea
+          autoFocus
+          value={draftText}
+          onChange={(e) => setDraftText(e.target.value)}
+          className="w-full rounded-md border border-default bg-input px-2.5 py-1.5 text-[0.8125rem] text-heading resize-y min-h-[44px] max-h-[140px] focus:outline-none focus:border-accent focus:ring-1 focus:ring-accent/30"
+          rows={2}
+        />
+        <input
+          type="text"
+          value={draftSummary}
+          onChange={(e) => setDraftSummary(e.target.value)}
+          placeholder="Short label (e.g. 'rules out tenant/license')"
+          className="mt-1.5 w-full rounded-md border border-default bg-input px-2.5 py-1 text-[0.75rem] text-heading placeholder:text-muted-foreground focus:outline-none focus:border-accent focus:ring-1 focus:ring-accent/30"
+        />
+        <div className="mt-1.5 flex items-center gap-2">
+          <button
+            onClick={handleSave}
+            disabled={busy || !draftText.trim()}
+            className="flex items-center gap-1 rounded-md bg-accent px-2.5 py-1 text-[0.75rem] font-medium text-white disabled:opacity-40 hover:bg-accent-hover transition-colors"
+          >
+            <Check size={11} /> Save
+          </button>
+          <button
+            onClick={handleCancel}
+            disabled={busy}
+            className="text-[0.75rem] text-muted-foreground hover:text-heading"
+          >
+            Cancel
+          </button>
+        </div>
+      </div>
+    )
+  }
+
+  return (
+    <div
+      className={cn(
+        'group rounded-lg border-l-[3px] border-l-success border border-success/25 bg-success-dim/20 p-3 mb-2',
+        busy && 'opacity-60',
+      )}
+    >
+      <div className="flex items-start gap-2">
+        <div className="mt-0.5 flex h-4 w-4 shrink-0 items-center justify-center rounded-full border border-dashed border-success">
+          <Check size={9} className="text-success" />
+        </div>
+        <div className="min-w-0 flex-1">
+          <div className="text-[0.8125rem] text-heading leading-relaxed">{fact.text}</div>
+          <div className="mt-1 text-[0.6875rem] text-muted-foreground">
+            <span>{provenanceLabel}</span>
+            {fact.source_summary && (
+              <>
+                <span className="mx-1">·</span>
+                <span className="italic">{fact.source_summary}</span>
+              </>
+            )}
+          </div>
+        </div>
+        <div className="flex shrink-0 items-center gap-1 opacity-0 group-hover:opacity-100 transition-opacity">
+          {fact.editable && (
+            <button
+              onClick={() => setEditing(true)}
+              disabled={busy}
+              className="p-1 rounded text-muted-foreground hover:text-heading hover:bg-elevated/40 transition-colors"
+              title="Edit fact"
+            >
+              <Pencil size={11} />
+            </button>
+          )}
+          <button
+            onClick={handleDelete}
+            disabled={busy}
+            className="p-1 rounded text-muted-foreground hover:text-danger hover:bg-elevated/40 transition-colors"
+            title="Remove fact"
+          >
+            {busy ? <X size={11} /> : <Trash2 size={11} />}
+          </button>
+        </div>
+      </div>
+    </div>
+  )
+}
+
+export default WhatWeKnowItem