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/preload/bridge.ts

@@ -1,4 +1,5 @@
 import { contextBridge, ipcRenderer } from "electron/renderer";
+import type { IpcRendererEvent } from "electron";
 import type {
   CreatePublishJobResponse,
   DesktopAccountInfo,
@@ -41,6 +42,17 @@ const desktopBridge = {
       ipcRenderer.invoke("desktop:runtime-session-sync", session) as Promise<null>,
     releaseRuntimeSession: (revoke?: boolean) =>
       ipcRenderer.invoke("desktop:runtime-session-release", revoke) as Promise<null>,
+    onRuntimeInvalidated: (
+      listener: (event: { reason: "account-health"; at: number }) => void,
+    ) => {
+      const wrapped = (_event: IpcRendererEvent, payload: { reason: "account-health"; at: number }) => {
+        listener(payload);
+      };
+      ipcRenderer.on("desktop:runtime-invalidated", wrapped);
+      return () => {
+        ipcRenderer.off("desktop:runtime-invalidated", wrapped);
+      };
+    },
   },
 };