feat(flywheel-c2-c3): C2 hasType4接真實API + C3 WebSocket指數退避重連

C2: flywheel_stats_service 加 type4_count query → API 回傳
    flywheel-diagram.tsx hasType4 改由 type4Count prop 驅動（非 false）
    flywheel-kpi-card.tsx 傳入 type4Count={flowData?.type4_count}

C3: WebSocket onclose 加指數退避重連 (1s→2s→4s→最大30s)
    cancelled 旗標確保 unmount 後不重連
    wsRetryTimer 加入 cleanup

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

apps/api/src/services/flywheel_stats_service.py

@@ -79,6 +79,7 @@ class FlywheelMetrics:
         self.node_stats = node_stats
         self.current_flow = current_flow
         self.computed_at = computed_at
+        self.type4_count: int = 0  # TYPE-4 incidents 數（ADR-073-C C2）
 
     def to_prometheus_lines(self) -> str:
         """輸出 Prometheus text format"""
@@ -115,6 +116,7 @@ class FlywheelMetrics:
         return {
             "nodes": self.node_stats,
             "current_flow": self.current_flow,
+            "type4_count": self.type4_count,
             "computed_at": self.computed_at.isoformat(),
         }
 
@@ -162,9 +164,10 @@ class FlywheelStatsService:
             today_processed,
             node_stats,
             current_flow,
+            type4_count,
         ) = await self._incident_stats(now)
 
-        return FlywheelMetrics(
+        metrics = FlywheelMetrics(
             playbook_count=playbook_count,
             execution_success_rate=execution_success_rate,
             km_unvectorized_count=km_unvectorized_count,
@@ -177,6 +180,8 @@ class FlywheelStatsService:
             current_flow=current_flow,
             computed_at=now,
         )
+        metrics.type4_count = type4_count
+        return metrics
 
     # ------------------------------------------------------------------
     # Internal helpers
@@ -274,6 +279,16 @@ class FlywheelStatsService:
                 )
                 incidents_stuck = stuck_q.scalar_one_or_none() or 0
 
+                # TYPE-4 Incident 數（ADR-073-C C2 — 供前端 hasType4 判斷）
+                # 2026-04-12 ogt
+                type4_q = await db.execute(
+                    select(func.count()).where(
+                        IncidentRecord.notification_type == "TYPE-4",
+                        IncidentRecord.status == IncidentStatus.INVESTIGATING.value,
+                    )
+                )
+                type4_count = type4_q.scalar_one_or_none() or 0
+
                 # 今日處理數
                 today_q = await db.execute(
                     select(func.count()).where(
@@ -355,11 +370,11 @@ class FlywheelStatsService:
                 },
             }
 
-            return alertname_null_rate, incidents_stuck, today_processed, node_stats, current_flow
+            return alertname_null_rate, incidents_stuck, today_processed, node_stats, current_flow, type4_count
 
         except Exception:
             logger.exception("flywheel_stats_incident_error")
-            return 0.0, 0, 0, {n: {"status": "unknown"} for n in FLYWHEEL_NODES}, []
+            return 0.0, 0, 0, {n: {"status": "unknown"} for n in FLYWHEEL_NODES}, [], 0
 
 
 def _status_to_node(status: str) -> str:

apps/web/src/components/dashboard/flywheel-diagram.tsx

@@ -24,6 +24,8 @@ interface FlywheelDiagramProps {
   currentFlow?: FlowItem[]
   /** active node names from node_stats */
   activeNodes?: Record<string, { status: string }>
+  /** TYPE-4 active incident count from API (ADR-073-C C2) */
+  type4Count?: number
 }
 
 const NODES = [
@@ -44,7 +46,7 @@ function toSVG(pct: { x: number; y: number }) {
   return { cx: (pct.x / 100) * W, cy: (pct.y / 100) * H }
 }
 
-export function FlywheelDiagram({ currentFlow = [], activeNodes = {} }: FlywheelDiagramProps) {
+export function FlywheelDiagram({ currentFlow = [], activeNodes = {}, type4Count = 0 }: FlywheelDiagramProps) {
   // Count active incidents per node
   const nodeCounts: Record<string, number> = {}
   for (const f of currentFlow) {
@@ -52,7 +54,7 @@ export function FlywheelDiagram({ currentFlow = [], activeNodes = {} }: Flywheel
   }
 
   const hasType3 = currentFlow.some(f => f.current_node === 'reasoning' || f.current_node === 'execution')
-  const hasType4 = false // TYPE-4 shown when diagnosis node has stuck items
+  const hasType4 = type4Count > 0
 
   // Build arc path through nodes in order
   const pts = NODES.map(n => toSVG(n))

apps/web/src/components/dashboard/flywheel-kpi-card.tsx

@@ -31,7 +31,7 @@ interface FlywheelSummary {
 
 export function FlywheelKPICard() {
   const [data, setData] = useState<FlywheelSummary | null>(null)
-  const [flowData, setFlowData] = useState<{ current_flow: FlowItem[]; nodes: Record<string, { status: string }> } | null>(null)
+  const [flowData, setFlowData] = useState<{ current_flow: FlowItem[]; nodes: Record<string, { status: string }>; type4_count?: number } | null>(null)
   const [error, setError] = useState(false)
   const wsRef = useRef<WebSocket | null>(null)
 
@@ -55,14 +55,18 @@ export function FlywheelKPICard() {
 
     load()
 
-    // C3: WebSocket — upgrades from polling when available
+    // C3: WebSocket — upgrades from polling when available, with reconnect (ADR-073-C C3)
+    // 指數退避重連：1s → 2s → 4s → 8s → 最大 30s
+    let wsRetryDelay = 1000
+    let wsRetryTimer: ReturnType<typeof setTimeout> | null = null
+
     const connectWS = () => {
-      if (!WS_BASE) return
+      if (!WS_BASE || cancelled) return
       const ws = new WebSocket(`${WS_BASE}/api/v1/stats/flywheel/ws`)
       wsRef.current = ws
 
       ws.onopen = () => {
-        // WS connected — stop HTTP polling
+        wsRetryDelay = 1000  // 連線成功 — 重置退避
         if (pollId) { clearInterval(pollId); pollId = null }
       }
       ws.onmessage = (e) => {
@@ -75,10 +79,14 @@ export function FlywheelKPICard() {
         } catch { /* ignore malformed */ }
       }
       ws.onclose = () => {
-        // WS closed — fall back to polling
-        if (!cancelled && !pollId) {
-          pollId = setInterval(load, 30_000)
-        }
+        if (cancelled) return
+        // 退回 HTTP polling
+        if (!pollId) pollId = setInterval(load, 30_000)
+        // 指數退避重連
+        wsRetryTimer = setTimeout(() => {
+          wsRetryDelay = Math.min(wsRetryDelay * 2, 30_000)
+          connectWS()
+        }, wsRetryDelay)
       }
       ws.onerror = () => ws.close()
     }
@@ -90,6 +98,7 @@ export function FlywheelKPICard() {
     return () => {
       cancelled = true
       if (pollId) clearInterval(pollId)
+      if (wsRetryTimer) clearTimeout(wsRetryTimer)
       wsRef.current?.close()
     }
   }, [])
@@ -175,6 +184,7 @@ export function FlywheelKPICard() {
         <FlywheelDiagram
           currentFlow={flowData?.current_flow ?? []}
           activeNodes={flowData?.nodes ?? {}}
+          type4Count={flowData?.type4_count ?? 0}
         />
       </div>