feat(coding-runtime): add managed Pi extension host

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

@@ -24,6 +24,7 @@ export interface PiConversationWorker {
     command: PiRpcCommand,
     options?: PiRpcRequestOptions,
   ): Promise<PiRpcResponse<T>>;
+  send(command: PiRpcCommand): Promise<void>;
   subscribe(listener: (event: PiRpcEvent) => void): () => void;
   subscribeInvalidation(listener: (error: PiProcessError) => void): () => void;
   stop(): Promise<PiWorkerStopResult>;
@@ -365,6 +366,18 @@ export class PiWorkerPool {
     }
   }
 
+  async send(conversationId: string, command: PiRpcCommand): Promise<void> {
+    let record = this.workers.get(conversationId);
+    if (!record || record.state === 'crashed') throw new Error('Conversation worker is not available');
+    if (record.rebuildFlight) record = await record.rebuildFlight;
+    await record.worker.send(command);
+  }
+
+  getActiveRun(conversationId: string): { runId: string; generation: number } | null {
+    const active = this.activeRuns.get(conversationId);
+    return active ? { ...active } : null;
+  }
+
   failTopLevel(conversationId: string, runId: string, error: Error): void {
     const active = this.activeRuns.get(conversationId);
     if (active?.runId === runId) {