feat(desktop): add hot view retain/release lifecycle and process metrics

Replace single-shot acquireHotView with retainHotView/releaseHotView
plus a minute-level reaper that closes views idle beyond 5 minutes and
never evicts a view while it still has live retainers. Wrap adapter
calls in try/finally so a failing publish/query still releases the
view. Sample process metrics every minute and expose hot-view policy
and process snapshot via the runtime snapshot for diagnostics.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/desktop-client/src/main/view-pool.ts

@@ -5,15 +5,54 @@ export interface HotViewHandle {
   accountId: string;
   view: ElectronWebContentsView;
   activatedAt: number;
+  lastReleasedAt: number | null;
+  retainCount: number;
 }
 
 const hotViews = new Map<string, HotViewHandle>();
+const HOT_VIEW_IDLE_TTL_MS = 5 * 60_000;
+const HOT_VIEW_REAPER_INTERVAL_MS = 60_000;
+let reaperHandle: ReturnType<typeof setInterval> | null = null;
+
+function closeView(handle: HotViewHandle): void {
+  if (!handle.view.webContents.isDestroyed()) {
+    handle.view.webContents.close();
+  }
+}
+
+function touchHandle(handle: HotViewHandle): HotViewHandle {
+  handle.activatedAt = Date.now();
+  return handle;
+}
+
+function demoteViewInternal(accountId: string): boolean {
+  const handle = hotViews.get(accountId);
+  if (!handle) {
+    return false;
+  }
+
+  closeView(handle);
+  hotViews.delete(accountId);
+  return true;
+}
+
+export function startHotViewReaper(): void {
+  if (reaperHandle) {
+    return;
+  }
+
+  reaperHandle = setInterval(() => {
+    reapIdleHotViews();
+  }, HOT_VIEW_REAPER_INTERVAL_MS);
+  reaperHandle.unref?.();
+}
 
 export function acquireHotView(accountId: string): HotViewHandle {
+  startHotViewReaper();
+
   const existing = hotViews.get(accountId);
   if (existing) {
-    existing.activatedAt = Date.now();
-    return existing;
+    return touchHandle(existing);
   }
 
   const handle: HotViewHandle = {
@@ -26,26 +65,80 @@ export function acquireHotView(accountId: string): HotViewHandle {
       },
     }),
     activatedAt: Date.now(),
+    lastReleasedAt: Date.now(),
+    retainCount: 0,
   };
   hotViews.set(accountId, handle);
   return handle;
 }
 
-export function demoteView(accountId: string): void {
+export function retainHotView(accountId: string): HotViewHandle {
+  const handle = touchHandle(acquireHotView(accountId));
+  handle.retainCount += 1;
+  handle.lastReleasedAt = null;
+  return handle;
+}
+
+export function releaseHotView(accountId: string): void {
   const handle = hotViews.get(accountId);
   if (!handle) {
     return;
   }
 
-  if (!handle.view.webContents.isDestroyed()) {
-    handle.view.webContents.close();
+  if (handle.retainCount > 0) {
+    handle.retainCount -= 1;
+  }
+
+  if (handle.retainCount === 0) {
+    handle.lastReleasedAt = Date.now();
   }
-  hotViews.delete(accountId);
 }
 
-export function listHotViews(): Array<Pick<HotViewHandle, "accountId" | "activatedAt">> {
-  return [...hotViews.values()].map(({ accountId, activatedAt }) => ({
+export function demoteView(accountId: string): boolean {
+  const handle = hotViews.get(accountId);
+  if (!handle || handle.retainCount > 0) {
+    return false;
+  }
+
+  return demoteViewInternal(accountId);
+}
+
+export function reapIdleHotViews(
+  now = Date.now(),
+  idleTTLms = HOT_VIEW_IDLE_TTL_MS,
+): string[] {
+  const reclaimed: string[] = [];
+
+  for (const [accountId, handle] of hotViews.entries()) {
+    if (handle.retainCount > 0) {
+      continue;
+    }
+
+    const idleSince = handle.lastReleasedAt ?? handle.activatedAt;
+    if (now - idleSince < idleTTLms) {
+      continue;
+    }
+
+    if (demoteViewInternal(accountId)) {
+      reclaimed.push(accountId);
+    }
+  }
+
+  return reclaimed;
+}
+
+export function listHotViews(): Array<Pick<HotViewHandle, "accountId" | "activatedAt" | "lastReleasedAt" | "retainCount">> {
+  return [...hotViews.values()].map(({ accountId, activatedAt, lastReleasedAt, retainCount }) => ({
     accountId,
     activatedAt,
+    lastReleasedAt,
+    retainCount,
   }));
 }
+
+export function getHotViewPoolPolicy() {
+  return {
+    idleTTLms: HOT_VIEW_IDLE_TTL_MS,
+    reapIntervalMs: HOT_VIEW_REAPER_INTERVAL_MS,
+  };
+}