fix(backend): track Pi turn lifecycle

backend/test/pi-process-manager.test.ts

@@ -155,6 +155,34 @@ test("createFor does not prompt until start is called", async () => {
   mgr.teardown("sid-deferred");
 });
 
+test("a created runtime is active during configure/bootstrap", () => {
+  const child = recordingChild();
+  const mgr = new PiProcessManager(loadConfig({}), { spawnFn: () => child as any });
+  const runtime = mgr.createFor("starting-id", {});
+  expect(runtime.bridge.turnState()).toBe("running");
+  mgr.teardown("starting-id");
+});
+
+test("start reactivates the runtime before sending the prompt", () => {
+  const child = recordingChild();
+  const mgr = new PiProcessManager(loadConfig({}), { spawnFn: () => child as any });
+  const runtime = mgr.createFor("restart-id", {});
+  child.stdout.emit("data", `${JSON.stringify({ type: "agent_end", messages: [] })}\n`);
+  expect(runtime.bridge.turnState()).toBe("idle");
+  let stateAtWrite = runtime.bridge.turnState();
+  child.stdin.write = (data: unknown) => {
+    stateAtWrite = runtime.bridge.turnState();
+    child._writes.push(String(data));
+    return true;
+  };
+
+  mgr.start("restart-id", runtime, { question: "q" });
+
+  expect(stateAtWrite).toBe("running");
+  expect(runtime.bridge.turnState()).toBe("running");
+  mgr.teardown("restart-id");
+});
+
 test("production spawn uses explicit Pi path and passes portable data root without rewriting PATH", async () => {
   vi.stubEnv("PATH", "/usr/local/bin:/usr/bin");
   vi.stubEnv("PI_PROVIDER_API_KEY", "provider-secret");