refactor(scheduler): split 15s tick into 4 independent intervals

Split the single 15s setInterval in scheduler.ts (6 serial jobs) into 4
independent schedulers so a slow job no longer stalls the others:

- scheduler-heartbeat.ts (15s): wake eligible agents, CEO bootstrap,
  schedule automation trigger
- scheduler-lock-recovery.ts (60s): stale task-lock recovery and stale
  workspace-lock release
- scheduler-idle-automation.ts (60s): idle-agent automation dispatch
- scheduler-housekeeping.ts (300s): monthly budget reset, expired budget
  incident auto-close, stale review sweep, expired wakeup purge

scheduler.ts is now a thin composer exposing startAllSchedulers /
stopAllSchedulers. Bootstrap and service-graph updated accordingly.
Business logic, error isolation, and atomic actions preserved.

src/main/service-graph.ts

@@ -321,7 +321,7 @@ export function createServiceGraph({
       shouldQuit: () => isQuittingRef.current,
       onBeforeQuit: () => {
         isQuittingRef.current = true;
-        orchestrationService?.stopHeartbeatScheduler();
+        orchestrationService?.stopAllSchedulers();
         automationService?.destroy();
         apiServerRef.current?.stop();
         apiServerRef.current = null;