fix(l1): actually wire Tasks 14-15 (prior commit ad9c4c8 was committed broken)

ad9c4c8 committed with TSC_EXIT=2 (I batched the commit with its own failing
verification). Two regressions, now fixed and tsc -b + eslint verified (TSC=0,
ESLINT=0):
- L1WalkTreeVariant.tsx: the ai_build JSX branch referenced isAiBuild/node/
  nodeLoading/nodeError/advanceNode/isTerminalNode that were never declared (the
  import + state Edits had silently failed). Add the import (useEffect/useCallback,
  TreeNode) and the state/effect/advanceNode/isTerminalNode block.
- L1Dashboard.tsx: had reverted to the original (no dispatch). Re-add outcome
  dispatch as minimal edits on the real page (matched/build->walker; suggest->
  use-flow/build-new; out_of_scope->escalate-without-walk).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/components/l1/L1WalkTreeVariant.tsx

@@ -1,8 +1,8 @@
-import { useState } from 'react'
+import { useState, useEffect, useCallback } from 'react'
 import { ChevronLeft } from 'lucide-react'
 import { Link } from 'react-router-dom'
 import { l1Api } from '@/api/l1'
-import type { WalkSession } from '@/types/l1'
+import type { TreeNode, WalkSession } from '@/types/l1'
 import { EscalateModal, ResolveModal } from '@/components/l1/WalkModals'
 
 interface Props {
@@ -16,6 +16,59 @@ export function L1WalkTreeVariant({ session, onSessionUpdate, onDone }: Props) {
   const [showEscalate, setShowEscalate] = useState(false)
   const [note, setNote] = useState('')
 
+  // Phase 2A: ai_build sessions are walked node-by-node against /next-node
+  // (real AI-generated decision tree), not the synthetic stepping below.
+  const isAiBuild = session.session_kind === 'ai_build'
+  const [node, setNode] = useState<TreeNode | null>(null)
+  const [nodeLoading, setNodeLoading] = useState(false)
+  const [nodeError, setNodeError] = useState<string | null>(null)
+
+  useEffect(() => {
+    if (!isAiBuild || session.status !== 'active') return
+    let cancelled = false
+    setNodeLoading(true)
+    l1Api
+      .nextNode(session.id, {})
+      .then((r) => {
+        if (!cancelled) setNode(r.node)
+      })
+      .catch(() => {
+        if (!cancelled) setNodeError('Could not generate the next step.')
+      })
+      .finally(() => {
+        if (!cancelled) setNodeLoading(false)
+      })
+    return () => {
+      cancelled = true
+    }
+  }, [isAiBuild, session.id, session.status])
+
+  const advanceNode = useCallback(
+    async (body: { answer?: 'yes' | 'no'; acknowledged?: boolean }) => {
+      if (!node) return
+      setNodeLoading(true)
+      setNodeError(null)
+      try {
+        const r = await l1Api.nextNode(session.id, {
+          node_id: node.id,
+          node_text: node.text,
+          ...body,
+        })
+        setNode(r.node)
+      } catch {
+        setNodeError('Could not generate the next step.')
+      } finally {
+        setNodeLoading(false)
+      }
+    },
+    [node, session.id],
+  )
+
+  const isTerminalNode =
+    node?.node_type === 'resolved' ||
+    node?.node_type === 'escalate' ||
+    node?.node_type === 'needs_review'
+
   // Phase 1: we don't have the live flow-tree fetch wired up here yet
   // (the tree-navigation pages have their own loader). The walker shows the
   // walked-path side panel, advance buttons stubbed for now — Phase 2 wires