fix(dashboard): auto-submit FlowPilot session when prefill from dashboard

When user types a problem on the dashboard and hits Enter, skip the
intake form and start the session immediately — no double-enter.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/pages/FlowPilotSessionPage.tsx

@@ -1,4 +1,4 @@
-import { useEffect, useState } from 'react'
+import { useEffect, useRef, useState } from 'react'
 import { useParams, useSearchParams, useLocation } from 'react-router-dom'
 import { Sparkles, Loader2 } from 'lucide-react'
 import { useFlowPilotSession } from '@/hooks/useFlowPilotSession'
@@ -13,6 +13,15 @@ export default function FlowPilotSessionPage() {
   const prefill = (location.state as { prefill?: string } | null)?.prefill || ''
   const isPickup = searchParams.get('pickup') === 'true'
   const fp = useFlowPilotSession()
+  const prefillHandledRef = useRef(false)
+
+  // Auto-submit when navigating from dashboard with prefilled problem
+  useEffect(() => {
+    if (prefill && !prefillHandledRef.current && !sessionId && !fp.session && !fp.isLoading) {
+      prefillHandledRef.current = true
+      fp.startSession({ intake_type: 'free_text', intake_content: { text: prefill } })
+    }
+  }, [prefill, sessionId, fp.session, fp.isLoading]) // eslint-disable-line react-hooks/exhaustive-deps
   const [pickingUp, setPickingUp] = useState(false)
 
   // Load existing session if ID in URL