feat: Scan state persists across navigation — resume polling on return

- URL, mode, tab, scan result persisted in localStorage
- Active scan_id stored — polling resumes when returning to page
- Scan results survive navigation to other SDK modules
- 'Scan laeuft noch...' shown when returning to in-progress scan
- Cleans up localStorage when scan completes or fails

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

admin-compliance/app/sdk/agent/page.tsx

@@ -21,15 +21,71 @@ const TABS: { id: AnalysisTab; label: string; desc: string }[] = [
 ]
 
 export default function AgentPage() {
-  const [url, setUrl] = useState('')
-  const [mode, setMode] = useState<AnalysisMode>('post_launch')
-  const [tab, setTab] = useState<AnalysisTab>('quick')
+  // Restore state from localStorage on mount
+  const [url, setUrl] = useState(() => typeof window !== 'undefined' ? localStorage.getItem('agent-scan-url') || '' : '')
+  const [mode, setMode] = useState<AnalysisMode>(() => (typeof window !== 'undefined' ? localStorage.getItem('agent-scan-mode') as AnalysisMode : null) || 'post_launch')
+  const [tab, setTab] = useState<AnalysisTab>(() => (typeof window !== 'undefined' ? localStorage.getItem('agent-scan-tab') as AnalysisTab : null) || 'quick')
   const [scanLoading, setScanLoading] = useState(false)
   const [scanError, setScanError] = useState<string | null>(null)
-  const [scanData, setScanData] = useState<any>(null)
+  const [scanData, setScanData] = useState<any>(() => {
+    if (typeof window === 'undefined') return null
+    try { const s = localStorage.getItem('agent-scan-result'); return s ? JSON.parse(s) : null } catch { return null }
+  })
   const [scanProgress, setScanProgress] = useState<string>('')
+  const [activeScanId, setActiveScanId] = useState<string>(() => typeof window !== 'undefined' ? localStorage.getItem('agent-scan-id') || '' : '')
   const { analyze, answerFollowUp, loading, error, result, history } = useAgentAnalysis()
 
+  // Persist state to localStorage
+  React.useEffect(() => { localStorage.setItem('agent-scan-url', url) }, [url])
+  React.useEffect(() => { localStorage.setItem('agent-scan-mode', mode) }, [mode])
+  React.useEffect(() => { localStorage.setItem('agent-scan-tab', tab) }, [tab])
+  React.useEffect(() => { if (scanData?.services) localStorage.setItem('agent-scan-result', JSON.stringify(scanData)) }, [scanData])
+
+  // Resume polling if scan was in progress when page was left
+  React.useEffect(() => {
+    if (!activeScanId || scanData?.services) return
+    let cancelled = false
+    setScanLoading(true)
+    setScanProgress('Scan laeuft noch...')
+    const poll = async () => {
+      while (!cancelled) {
+        await new Promise(r => setTimeout(r, 5000))
+        try {
+          const res = await fetch(`/api/sdk/v1/agent/scan?scan_id=${activeScanId}`)
+          if (!res.ok) continue
+          const data = await res.json()
+          if (data.progress) setScanProgress(data.progress)
+          if (data.status === 'completed' && data.result) {
+            setScanData(data.result)
+            setScanProgress('')
+            setScanLoading(false)
+            localStorage.setItem('agent-scan-result', JSON.stringify(data.result))
+            localStorage.removeItem('agent-scan-id')
+            setActiveScanId('')
+            return
+          }
+          if (data.status === 'failed') {
+            setScanError(data.error || 'Scan fehlgeschlagen')
+            setScanProgress('')
+            setScanLoading(false)
+            localStorage.removeItem('agent-scan-id')
+            setActiveScanId('')
+            return
+          }
+          if (data.status === 'not_found') {
+            setScanProgress('')
+            setScanLoading(false)
+            localStorage.removeItem('agent-scan-id')
+            setActiveScanId('')
+            return
+          }
+        } catch { /* retry */ }
+      }
+    }
+    poll()
+    return () => { cancelled = true }
+  }, []) // eslint-disable-line react-hooks/exhaustive-deps
+
   const handleSubmit = async (e: React.FormEvent) => {
     e.preventDefault()
     if (!url.trim()) return
@@ -51,6 +107,8 @@ export default function AgentPage() {
         if (!startRes.ok) throw new Error(`Scan konnte nicht gestartet werden: ${startRes.status}`)
         const { scan_id } = await startRes.json()
         if (!scan_id) throw new Error('Keine Scan-ID erhalten')
+        setActiveScanId(scan_id)
+        localStorage.setItem('agent-scan-id', scan_id)
 
         // Step 2: Poll for results
         let attempts = 0
@@ -68,6 +126,9 @@ export default function AgentPage() {
           if (pollData.status === 'completed' && pollData.result) {
             setScanData(pollData.result)
             setScanProgress('')
+            localStorage.setItem('agent-scan-result', JSON.stringify(pollData.result))
+            localStorage.removeItem('agent-scan-id')
+            setActiveScanId('')
             break
           }
           if (pollData.status === 'failed') {