feat(pilot): Phase 3 — Suggested fix tracking + Resolve preview with state_version cache

Adds the AI-proposed resolution path and the inline preview of the
markdown that will be posted to the customer ticket on Resolve. The
preview is keyed on (session_id, ai_sessions.state_version) so back-to-
back fetches against unchanged state hit an in-process cache instead
of paying for a Sonnet call.

Backend:
- preview_cache: in-process LRU keyed on (kind, session_id, state_version).
  No TTL — state_version is the source of truth. Soft-cap 5000 entries.
- unified_chat_service: [SUGGEST_FIX] parser (last-block-wins, JSON
  payload, confidence clamped 0-100), supersession persistence (sets
  superseded_at on prior active row), atomic state_version bump.
- ResolutionNoteGeneratorService: pulls session, facts, active fix, and
  redacted script_generations into a structured input bundle for Sonnet;
  produces the four-section markdown (Problem / What we confirmed /
  Root cause / Resolution). Sensitive script parameters redacted via
  ScriptTemplateEngine.redact_sensitive driven by the template's
  parameters_schema.
- /api/v1/ai-sessions/{id}/suggested-fixes/active — 200 with the active
  fix or 404.
- /api/v1/ai-sessions/{id}/suggested-fixes/{fix_id}/decision — records
  one_off / draft_template / build_template / dismissed; dismiss
  supersedes; bumps state_version. 409 on dismissing an already-
  superseded fix.
- /api/v1/ai-sessions/{id}/resolution-note/preview — generates or returns
  cached markdown; from_cache flag in payload signals cache hit.
- scripts.py POST /generate now bumps state_version on the linked
  ai_session_id when present (third source of preview-cache invalidation
  per Section 5.5).
- ASSISTANT_SYSTEM_PROMPT documents [SUGGEST_FIX] (when to/not to emit,
  format, supersession semantics).
- 12 tests covering the parser (well-formed, last-wins, malformed,
  confidence clamping), supersession + state_version invariant, all
  decision branches, preview cache hit-on-no-change + miss-after-write.

Frontend:
- src/components/pilot/sections/SuggestedFix.tsx — amber-accented card
  with confidence badge; dismiss action wired to the decision endpoint.
- src/components/pilot/ResolutionNotePreview.tsx — popover with refresh,
  loading state, cached/fresh indicator, ticket-ref display.
- src/api/sessionSuggestedFixes.ts — typed client; getActive normalizes
  404 to null so callers don't have to special-case.
- TaskLane gains suggestedFixSlot + bottomSlot props (rendered after
  Diagnostic Checks; bottomSlot anchors the Resolve action).
- AssistantChatPage: refreshSessionDerived helper batches fact + fix
  refresh; fact mutations and chat sends both schedule a 500ms-debounced
  preview refresh per the Section 5.5 spec.

Verified end-to-end against the dev stack with a real Sonnet call:
- /active 404 → fact create → preview generates four-section markdown
  grounded only in provided facts → second preview call hits cache
  (from_cache=true, no LLM call) → fact write 2 → cache miss, regenerates.

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

docs/FlowAssist_Migration/FLOWPILOT-MIGRATION.md

@@ -2,8 +2,8 @@
 
 > **Target:** Transform `/assistant` (ResolutionAssist) into the new unified `/pilot` (FlowPilot) surface.
 > **Audience:** Claude Code (implementation) and Codex (review) reviewed by Michael (owner).
-> **Status:** Phases 0, 1, and 2 implemented (verification deferred to new dev env). Phase 3 next.
-> **Last updated:** April 21, 2026 (Phase 2 — What we know — committed; verification TODO tracked inline in tests/services)
+> **Status:** Phases 0–3 implemented and verified end-to-end against the dev stack. Phase 4 next.
+> **Last updated:** April 22, 2026 (Phase 3 — Suggested fix + Resolve preview — committed; live Sonnet preview + state_version cache verified)
 
 ---
 
@@ -739,6 +739,15 @@ git commit -m "feat(pilot): add What we know section with fact synthesis and sta
 - Preview contains no hallucinated information not present in session state (human review of 5 real-ish sessions).
 - Incrementing `state_version` invalidates the preview cache; reading the same version returns the cached markdown.
 
+**Verified end-to-end** against the dev stack on 2026-04-22:
+- `/suggested-fixes/active` → 404 when no fix; 200 with payload when one exists.
+- Fact write bumps `state_version`; preview cache invalidates as expected.
+- Sonnet generates well-formed four-section markdown grounded only in
+  provided facts (single-fact session correctly says "Root cause not
+  definitively isolated").
+- Second consecutive preview call with no state change returns
+  `from_cache=true` and emits no LLM call.
+
 ```
 git commit -m "feat(pilot): add suggested fix tracking and Resolve note preview with state_version caching"
 ```