feat(KB-150): kill active agent sessions on global pause

- Add settings:updated event to TaskStore with previous/new settings payload
- Kill all active executor agent sessions when globalPause transitions false→true
- Kill all active triage specification sessions on global pause with clean status reset
- Track and dispose active merger session on global pause via onSession callback
- Add JSDoc documenting global pause behavior on executor and triage constructors

packages/engine/src/triage.ts

@@ -184,12 +184,36 @@ export class TriageProcessor {
   private activePollMs: number | null = null;
   private processing = new Set<string>();
   private wasGlobalPaused = false;
+  /** Active agent sessions per task, used to terminate on global pause. */
+  private activeSessions = new Map<string, { dispose: () => void }>();
+  /** Tasks that were aborted due to global pause (to avoid reporting as errors). */
+  private globalPauseAborted = new Set<string>();
 
+  /**
+   * @param store — Task store instance (also used to listen for `settings:updated` events)
+   * @param rootDir — Project root directory
+   * @param options — Processor configuration
+   *
+   * Listens for `settings:updated` events: when `globalPause` transitions from
+   * `false` to `true`, all active triage specification sessions are immediately
+   * terminated so the engine acts as a true emergency stop.
+   */
   constructor(
     private store: TaskStore,
     private rootDir: string,
     private options: TriageProcessorOptions = {},
-  ) {}
+  ) {
+    // When globalPause transitions from false → true, terminate all active triage sessions.
+    store.on("settings:updated", ({ settings, previous }) => {
+      if (settings.globalPause && !previous.globalPause) {
+        for (const [taskId, session] of this.activeSessions) {
+          triageLog.log(`Global pause — terminating triage session for ${taskId}`);
+          this.globalPauseAborted.add(taskId);
+          session.dispose();
+        }
+      }
+    });
+  }
 
   start(): void {
     if (this.running) return;
@@ -305,6 +329,9 @@ export class TriageProcessor {
           defaultThinkingLevel: settings.defaultThinkingLevel,
         });
 
+        // Register session so the global pause listener can terminate it
+        this.activeSessions.set(task.id, session);
+
         try {
           // Read attachment contents for inlining in prompt
           const { attachmentContents, imageContents } = await readAttachmentContents(
@@ -355,6 +382,7 @@ export class TriageProcessor {
             this.options.onSpecifyComplete?.(task);
           }
         } finally {
+          this.activeSessions.delete(task.id);
           await agentLogger.flush();
           session.dispose();
         }
@@ -370,6 +398,11 @@ export class TriageProcessor {
       // and specifyTask(). The file is gone, so just log and skip — no point retrying.
       if (err.code === "ENOENT") {
         triageLog.log(`${task.id} no longer exists — skipping`);
+      } else if (this.globalPauseAborted.has(task.id)) {
+        // Global pause — clear specifying status without reporting an error
+        this.globalPauseAborted.delete(task.id);
+        triageLog.log(`${task.id} aborted by global pause — clearing status`);
+        await this.store.updateTask(task.id, { status: null }).catch(() => {});
       } else {
         // Check if the error is a usage-limit error and trigger global pause
         if (this.options.usageLimitPauser && isUsageLimitError(err.message)) {