fix(backend): track Pi turn lifecycle

backend/src/bridge/session-bridge.ts

@@ -7,7 +7,10 @@ export type ClientEvent =
   | { type: "info"; [k: string]: any }
   | { type: "system_event"; [k: string]: any };
 
+export type TurnState = "idle" | "running" | "waiting" | "failed";
+
 export class SessionBridge {
+  private state: TurnState = "idle";
   private pending: any = null;
   // Pi (rpc-mode createDialogPromise) assegna a ogni ctx.ui.input un id RPC PROPRIO
   // (crypto.randomUUID) e correla extension_ui_response su quell'id — NON sull'id interno
@@ -23,7 +26,19 @@ export class SessionBridge {
         try { descriptor = JSON.parse(m.title as string); } catch { return; }
         this.pending = descriptor;
         this.pendingPiId = m.id as string | null;
+        this.state = "waiting";
         this.fan({ type: "ui_request", ui_request: descriptor });
+      } else if (
+        m.type === "message_end" &&
+        m.message?.role === "assistant" &&
+        m.message?.stopReason === "error"
+      ) {
+        this.state = "failed";
+        this.fan({
+          type: "info",
+          level: "error",
+          text: "Model request failed. Check provider connectivity, then Resume the session.",
+        });
       } else if (m.type === "extension_ui_request" && m.method === "notify") {
         this.fan({ type: "info", level: m.notifyType ?? "info", text: m.message ?? "" });
       } else if (m.type === "message_update" && m.assistantMessageEvent?.type === "text_delta") {
@@ -37,8 +52,10 @@ export class SessionBridge {
       } else if (m.type === "system_event") {
         this.fan(m as ClientEvent);
       } else if (m.type === "agent_end") {
+        if (this.state !== "failed" && !this.pending) this.state = "idle";
         this.fan({ type: "system_event", event: "agent_end" });
       } else if (m.type === "agent_start") {
+        this.state = "running";
         this.fan({ type: "system_event", event: "agent_start" });
       } else if (m.type === "turn_end") {
         this.fan({ type: "system_event", event: "turn_end" });
@@ -48,6 +65,10 @@ export class SessionBridge {
 
   private fan(e: ClientEvent) { for (const cb of this.cbs) cb(e); }
 
+  turnState(): TurnState { return this.state; }
+
+  beginTurn(): void { this.state = "running"; }
+
   onClientEvent(cb: (e: ClientEvent) => void): void { this.cbs.add(cb); }
 
   /** Eventi generati dal backend stesso (es. exit inatteso del child Pi), non da Pi. */
@@ -57,11 +78,15 @@ export class SessionBridge {
     // Correla sull'id RPC di Pi; `value` porta l'uiResponse (con l'id del descriptor) cosi'
     // il check interno del gate (resp.id === descriptor.id) regge.
     const piId = this.pendingPiId ?? uiResponse.id;
+    this.state = "running";
     this.rpc.send({ type: "extension_ui_response", id: piId, value: JSON.stringify(uiResponse) });
     if (this.pending && uiResponse.id === this.pending.id) { this.pending = null; this.pendingPiId = null; }
   }
 
-  steer(text: string): void { this.rpc.send({ type: "steer", message: text }); }
+  steer(text: string): void {
+    this.state = "running";
+    this.rpc.send({ type: "steer", message: text });
+  }
 
   pendingWidget(): object | null { return this.pending; }
 }