fix: add retry tolerance to frontend polling (H3)

A single transient network error (502, timeout) no longer kills the
polling loop. The frontend now tolerates up to 3 consecutive errors
before abandoning. Successful fetches reset the counter.

Also aligns frontend polling timeout (15 min) with backend timeout.

Ref #57 (H3, M5)

frontend/src/features/analysis/store.test.ts

@@ -154,17 +154,49 @@ describe('useAnalysisStore', () => {
     expect(store.currentAnalysis.status).toBe('FAILED')
   })
 
-  it('polling stops on fetch error', async () => {
+  it('polling retries on transient errors and stops after MAX_POLL_RETRIES', async () => {
     const job = { id: 'j1', status: 'PENDING', documentId: 'd1' }
     api.createAnalysis.mockResolvedValue(job)
     api.fetchAnalysis.mockRejectedValue(new Error('network'))
+    vi.spyOn(console, 'warn').mockImplementation(() => {})
     vi.spyOn(console, 'error').mockImplementation(() => {})
 
     const store = useAnalysisStore()
     await store.run('d1')
 
+    // First two errors: still polling
     await vi.advanceTimersByTimeAsync(2000)
+    expect(store.running).toBe(true)
+    await vi.advanceTimersByTimeAsync(2000)
+    expect(store.running).toBe(true)
 
+    // Third error: stops polling
+    await vi.advanceTimersByTimeAsync(2000)
+    expect(store.running).toBe(false)
+  })
+
+  it('polling resets error count on successful fetch', async () => {
+    const job = { id: 'j1', status: 'PENDING', documentId: 'd1' }
+    api.createAnalysis.mockResolvedValue(job)
+    vi.spyOn(console, 'warn').mockImplementation(() => {})
+
+    // Fail once, succeed, fail once — should NOT stop polling
+    api.fetchAnalysis
+      .mockRejectedValueOnce(new Error('network'))
+      .mockResolvedValueOnce({ ...job, status: 'RUNNING' })
+      .mockRejectedValueOnce(new Error('network'))
+      .mockResolvedValueOnce({ ...job, status: 'COMPLETED' })
+
+    const store = useAnalysisStore()
+    await store.run('d1')
+
+    await vi.advanceTimersByTimeAsync(2000) // error 1
+    expect(store.running).toBe(true)
+    await vi.advanceTimersByTimeAsync(2000) // success — resets counter
+    expect(store.running).toBe(true)
+    await vi.advanceTimersByTimeAsync(2000) // error 1 again
+    expect(store.running).toBe(true)
+    await vi.advanceTimersByTimeAsync(2000) // success — COMPLETED
     expect(store.running).toBe(false)
   })
 })

frontend/src/features/analysis/store.ts

@@ -10,7 +10,8 @@ export const useAnalysisStore = defineStore('analysis', () => {
   const error = ref<string | null>(null)
   const pollingInterval = ref<ReturnType<typeof setInterval> | null>(null)
   const pollingTimeout = ref<ReturnType<typeof setTimeout> | null>(null)
-  const MAX_POLLING_DURATION = 10 * 60 * 1000 // 10 minutes
+  const MAX_POLLING_DURATION = 15 * 60 * 1000 // 15 minutes — aligned with backend timeout
+  const MAX_POLL_RETRIES = 3
 
   const currentPages = computed<Page[]>(() => {
     if (!currentAnalysis.value?.pagesJson) return []
@@ -87,9 +88,11 @@ export const useAnalysisStore = defineStore('analysis', () => {
 
   function startPolling(id: string): void {
     stopPolling()
+    let consecutiveErrors = 0
     pollingInterval.value = setInterval(async () => {
       try {
         const updated = await api.fetchAnalysis(id)
+        consecutiveErrors = 0
         currentAnalysis.value = updated
         const idx = analyses.value.findIndex((a) => a.id === id)
         if (idx !== -1) analyses.value[idx] = updated
@@ -98,10 +101,14 @@ export const useAnalysisStore = defineStore('analysis', () => {
           running.value = false
         }
       } catch (e) {
-        error.value = (e as Error).message || 'Polling error'
-        console.error('Polling error', e)
-        stopPolling()
-        running.value = false
+        consecutiveErrors++
+        console.warn(`Polling error (${consecutiveErrors}/${MAX_POLL_RETRIES})`, e)
+        if (consecutiveErrors >= MAX_POLL_RETRIES) {
+          error.value = (e as Error).message || 'Polling error'
+          console.error('Polling abandoned after retries', e)
+          stopPolling()
+          running.value = false
+        }
       }
     }, 2000)
     pollingTimeout.value = setTimeout(() => {