feat(desktop): add monitor scheduler, Playwright CDP layer, and account health

Move monitor-task scheduling authority onto the client with a durable
file-backed queue that survives restart, drops stale cross-day tasks,
enforces per-platform serialism, and adapts global concurrency from
Electron process metrics. Publish tasks keep their existing FIFO.

Add a hidden Playwright CDP manager that attaches to Electron Chromium
on account session partitions, lets adapters opt into `executionMode:
"playwright"`, and leaves the existing hidden WebContentsView path in
place for current adapters.

Introduce an account-health subsystem with silent probes, projected
health/auth states, and IPC invalidation events so the renderer can
show accurate auth/probe status and verification timestamps.

Server-side, derive and forward title/business_date/scheduler_group_key/
question_text metadata on desktop task events so the local scheduler
can defer same-question fan-out before leasing.

apps/desktop-client/src/main/runtime-events.ts

@@ -0,0 +1,34 @@
+type RuntimeInvalidationReason = "account-health";
+
+type RuntimeInvalidationListener = (event: {
+  reason: RuntimeInvalidationReason;
+  at: number;
+}) => void;
+
+const listeners = new Set<RuntimeInvalidationListener>();
+
+export function emitRuntimeInvalidated(reason: RuntimeInvalidationReason): void {
+  const event = {
+    reason,
+    at: Date.now(),
+  } as const;
+
+  for (const listener of listeners) {
+    try {
+      listener(event);
+    } catch (error) {
+      console.warn("[desktop-runtime] invalidation listener failed", {
+        reason,
+        message: error instanceof Error ? error.message : String(error),
+      });
+    }
+  }
+}
+
+export function onRuntimeInvalidated(listener: RuntimeInvalidationListener): () => void {
+  listeners.add(listener);
+  return () => {
+    listeners.delete(listener);
+  };
+}
+