fix(resume): recover cleanly after Pi exits

backend/test/routes-sessions.test.ts

@@ -137,18 +137,21 @@ test.each(["running", "waiting"])(
   "POST resume preserves a %s runtime",
   async (state) => {
     let tornDown = false;
+    let cleared = false;
     const existing = { bridge: { turnState: () => state } } as any;
     const app = buildApp(loadConfig({ THT_HARNESS_DIR: "../harness" }), {
       mgr: {
         get: () => existing,
         teardown: () => { tornDown = true; },
       } as any,
+      hub: { clear: () => { cleared = true; } } as any,
       thtRunner: {} as any,
       getSettings: () => ({ workspace: "psd" }) as any,
     });
     const response = await app.inject({ method: "POST", url: "/sessions/s1/resume" });
     expect(response.json()).toEqual({ id: "s1", alreadyActive: true });
     expect(tornDown).toBe(false);
+    expect(cleared).toBe(false);
   },
 );
 
@@ -166,6 +169,10 @@ test.each(["idle", "failed"])(
         configure: async () => {},
         start: () => order.push("start"),
       } as any,
+      hub: {
+        clear: (id: string) => order.push(`clear:${id}`),
+        publish: () => {},
+      } as any,
       thtRunner: {
         sessionShow: async () => ({
           status: "open", archived: false,
@@ -179,10 +186,95 @@ test.each(["idle", "failed"])(
     const response = await app.inject({ method: "POST", url: "/sessions/s1/resume" });
     await new Promise((resolve) => setImmediate(resolve));
     expect(response.json()).toEqual({ id: "s1" });
-    expect(order).toEqual(["teardown:s1", "reopen", "create", "start"]);
+    expect(order).toEqual(["teardown:s1", "clear:s1", "reopen", "create", "start"]);
   },
 );
 
+test("POST resume without a runtime clears stale SSE state before cold start", async () => {
+  const order: string[] = [];
+  let createOptions: any;
+  const newRuntime = { bridge: { onClientEvent: () => {}, emitClientEvent: () => {} } } as any;
+  const app = buildApp(loadConfig({ THT_HARNESS_DIR: "../harness" }), {
+    mgr: {
+      get: () => undefined,
+      createFor: (_id: string, options: any) => {
+        createOptions = options;
+        order.push("create");
+        return newRuntime;
+      },
+      configure: async () => {},
+      start: () => order.push("start"),
+    } as any,
+    hub: {
+      clear: (id: string) => order.push(`clear:${id}`),
+      publish: () => {},
+    } as any,
+    thtRunner: {
+      sessionShow: async () => ({
+        status: "open", archived: false,
+        provider: "local-qwen", model: "qwen3.6-35b-a3b", thinking: "low",
+      }),
+      reopenSession: async () => order.push("reopen"),
+    } as any,
+    readiness: { ensure: async () => ({ ok: true }) } as any,
+    getSettings: () => ({ workspace: "local", thinking: "medium" }) as any,
+  });
+
+  const response = await app.inject({ method: "POST", url: "/sessions/crashed/resume" });
+  await new Promise((resolve) => setImmediate(resolve));
+
+  expect(response.json()).toEqual({ id: "crashed" });
+  expect(order).toEqual(["clear:crashed", "reopen", "create", "start"]);
+  expect(createOptions).toMatchObject({
+    provider: "local-qwen", model: "qwen3.6-35b-a3b", thinking: "low", mode: "resume",
+  });
+});
+
+test("POST resume keeps an idle runtime stream attached when the manifest is read-only", async () => {
+  let tornDown = false;
+  let cleared = false;
+  const app = buildApp(loadConfig({ THT_HARNESS_DIR: "../harness" }), {
+    mgr: {
+      get: () => ({ bridge: { turnState: () => "idle" } }),
+      teardown: () => { tornDown = true; },
+    } as any,
+    hub: { clear: () => { cleared = true; } } as any,
+    thtRunner: {
+      sessionShow: async () => ({ status: "finalized", archived: false }),
+    } as any,
+    getSettings: () => ({ workspace: "local" }) as any,
+  });
+
+  const response = await app.inject({ method: "POST", url: "/sessions/s1/resume" });
+
+  expect(response.statusCode).toBe(409);
+  expect(tornDown).toBe(false);
+  expect(cleared).toBe(false);
+});
+
+test("POST resume keeps a failed runtime stream attached when readiness fails", async () => {
+  let tornDown = false;
+  let cleared = false;
+  const app = buildApp(loadConfig({ THT_HARNESS_DIR: "../harness" }), {
+    mgr: {
+      get: () => ({ bridge: { turnState: () => "failed" } }),
+      teardown: () => { tornDown = true; },
+    } as any,
+    hub: { clear: () => { cleared = true; } } as any,
+    thtRunner: {
+      sessionShow: async () => ({ status: "open", archived: false }),
+    } as any,
+    readiness: { ensure: async () => ({ ok: false, error: "not ready" }) } as any,
+    getSettings: () => ({ workspace: "local" }) as any,
+  });
+
+  const response = await app.inject({ method: "POST", url: "/sessions/s1/resume" });
+
+  expect(response.statusCode).toBe(503);
+  expect(tornDown).toBe(false);
+  expect(cleared).toBe(false);
+});
+
 test("POST /sessions/:id/response inoltra al bridge (no error)", async () => {
   const app = buildApp(loadConfig({ THT_HARNESS_DIR: "../harness" }), {
     thtRunner: {