fix(l1): resolve PR #193 frontend review findings (2a,2b,3,4,5,7)

Mounts L1EscalationsSection on EscalationQueuePage (Finding 2a — it was never
rendered) and renders the correct fields: step.question ?? step.text, timeAgo,
and the session problem_text (Finding 2b). ProposalDetail gates the /pilot link
on source_session_id and shows an L1-source block for l1_session_id-sourced
proposals (Finding 3 — was a broken /pilot/null link). Collapses the three
near-identical intake handlers into one runIntake: "Use this flow" now passes
near_miss.flow_id (Finding 4 — it previously re-suggested forever) and a
navigate guard prevents /l1/walk/undefined; out_of_scope gains a "Walk it
ad-hoc" button (Finding 5). Aligns L1-category permissions to owner+admin:
usePermissions.canManageAccount includes account admins, User.account_role TS
type gains 'admin', and a new ProtectedRoute requireAccountManager guard fronts
the route (Finding 7). Drops the unused NextNodeRequest.acknowledged field.

tsc -b + eslint + vite build clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/pages/EscalationQueuePage.tsx

@@ -1,13 +1,14 @@
 import { useState } from 'react'
 import { AlertTriangle } from 'lucide-react'
 import { EscalationQueue, EscalationMetricCard } from '@/components/flowpilot'
+import { L1EscalationsSection } from '@/components/l1/L1EscalationsSection'
 
 export default function EscalationQueuePage() {
   const [count, setCount] = useState<number | null>(null)
 
   return (
-    <div className="mx-auto max-w-4xl p-6">
-      <div className="flex items-center gap-3 mb-6">
+    <div className="mx-auto max-w-4xl p-6 space-y-6">
+      <div className="flex items-center gap-3">
         <span className="flex h-8 w-8 items-center justify-center rounded-lg bg-warning-dim">
           <AlertTriangle size={16} className="text-warning" />
         </span>
@@ -24,6 +25,10 @@ export default function EscalationQueuePage() {
       <EscalationMetricCard period="30d" />
 
       <EscalationQueue onCountChange={setCount} />
+
+      {/* L1 AI-build handoffs (GET /l1/escalations). Renders nothing when empty,
+          so engineers without L1 escalations see no change. */}
+      <L1EscalationsSection />
     </div>
   )
 }