fix(pi): converge worker failures and thinking state

electron/coding-runtime/pi/subagent.ts

@@ -2,6 +2,7 @@ import { randomUUID } from 'node:crypto';
 
 import type { PublicUsage, SubagentDetailsV1 } from '../contracts';
 import { PiProcessBudget, type PiProcessLease } from './worker-pool';
+import type { PiWorkerStopReason } from './worker-process';
 
 export type PiSubagentMode = SubagentDetailsV1['mode'];
 export type PiSubagentToolProfile = SubagentDetailsV1['tasks'][number]['toolProfile'];
@@ -43,7 +44,7 @@ export interface PiSubagentChild {
     signal: AbortSignal,
     onProgress?: (summary: string) => void,
   ): Promise<PiSubagentChildResult>;
-  stop(): Promise<void>;
+  stop(reason: PiWorkerStopReason): Promise<void>;
 }
 
 export interface PiSubagentDispatchResult {
@@ -368,6 +369,7 @@ export class PiSubagentScheduler {
     let releaseChild: (() => void) | undefined;
     let processLease: PiProcessLease | undefined;
     let child: PiSubagentChild | undefined;
+    let stopReason: PiWorkerStopReason = 'subagent_complete';
     try {
       releaseChild = await this.childPermits.acquire(record.controller.signal);
       processLease = await this.acquireProcessLease(record.controller.signal);
@@ -394,12 +396,13 @@ export class PiSubagentScheduler {
     } catch (error) {
       const aborted = record.controller.signal.aborted
         || (error instanceof PiSubagentChildError && error.code === 'SUBAGENT_ABORTED');
+      if (aborted) stopReason = 'subagent_abort';
       projected.status = aborted ? 'aborted' : 'error';
       projected.errorCode = publicErrorCode(error, aborted);
     } finally {
       if (child) {
         record.children.delete(child);
-        await child.stop().catch(() => undefined);
+        await child.stop(stopReason).catch(() => undefined);
       }
       processLease?.release();
       releaseChild?.();