feat: add Pi conversation worker pool

electron/coding-runtime/pi/worker-process.ts

@@ -177,6 +177,7 @@ export class PiWorkerProcess {
   private stopping = false;
   private stopPromise: Promise<PiWorkerStopResult> | null = null;
   private exitResult: Promise<{ code: number | null; signal: NodeJS.Signals | null }> | null = null;
+  private readonly invalidationListeners = new Set<(error: PiProcessError) => void>();
 
   constructor(options: PiWorkerProcessOptions) {
     this.options = options;
@@ -314,6 +315,11 @@ export class PiWorkerProcess {
     return this.rpc.subscribe(listener);
   }
 
+  subscribeInvalidation(listener: (error: PiProcessError) => void): () => void {
+    this.invalidationListeners.add(listener);
+    return () => this.invalidationListeners.delete(listener);
+  }
+
   stop(): Promise<PiWorkerStopResult> {
     if (!this.stopPromise) this.stopPromise = this.performStop();
     return this.stopPromise;
@@ -345,6 +351,15 @@ export class PiWorkerProcess {
     this.invalidation = error;
     this.rpc?.invalidate(error);
     this.generationValue += 1;
+    for (const listener of this.invalidationListeners) {
+      try {
+        listener(error);
+      } catch (listenerError) {
+        this.appendDiagnostic(
+          `[invalidation-listener] ${listenerError instanceof Error ? listenerError.message : String(listenerError)}\n`,
+        );
+      }
+    }
   }
 
   private appendDiagnostic(source: string): void {