feat: pet chat window replaces the Sagi panel; Windows pane attach no longer crashes the server

- Sagi: clicking the pet opens its chat window directly (PetChat + SagiInfo
  status strip, Needs you, Mute / Clear alerts); SagiPanel removed.
- Chat view answers Claude's unnumbered folder-trust prompt (parseBareMenu).
- pty-attach: resize/write after a Windows attach exited, and node-pty's pipe
  errors, no longer throw out of the WebSocket handler.
- restart-helper: the server started by an update logs to
  data/agenthub-server.log instead of discarding its output.

server/__tests__/pty-attach.test.js

@@ -204,6 +204,45 @@ describe("pty-attach", () => {
     assert.deepEqual(JSON.parse(a.__sent.at(-1).data), { type: "lead" });
   });
 
+  it("survives a stopped pane: pipe errors, typing and resizes after the attach exited", () => {
+    // Windows node-pty re-throws a read-pipe error nobody listens for, and its
+    // write pipe has no listener at all: Stop (kill-session) ended the attach
+    // with EPIPE and the uncaught error killed the whole dashboard.
+    const ptys = [];
+    ptyAttach.__setSpawnImpl(() => {
+      const p = makeFakePty();
+      p.on = (evt, fn) => p.__emitter.on(evt, fn);
+      p._agent = { inSocket: new EventEmitter() };
+      p.resize = () => {
+        if (p.__gone) throw new Error("Cannot resize a pty that has already exited");
+      };
+      p.write = () => {
+        if (p.__gone) throw new Error("write EPIPE");
+      };
+      ptys.push(p);
+      return p;
+    });
+    const a = makeFakeWs();
+    const b = makeFakeWs();
+    a.close = b.close = () => {};
+    ptyAttach.attach(a, "agenthub-lane-1", { cols: 80, rows: 24 });
+    ptyAttach.attach(b, "agenthub-lane-1", { cols: 80, rows: 24 });
+
+    const epipe = Object.assign(new Error("read EPIPE"), { code: "EPIPE" });
+    assert.doesNotThrow(() => ptys[0].__emitter.emit("error", epipe));
+    assert.doesNotThrow(() => ptys[0]._agent.inSocket.emit("error", epipe));
+
+    ptys[0].__gone = true;
+    ptys[0].__emitter.emit("exit", { exitCode: 1 }); // a's close event not yet in
+    const msg = (ws, data, binary) => ws.__emitter.emit("message", Buffer.from(data), { binary });
+    assert.doesNotThrow(() =>
+      msg(b, JSON.stringify({ type: "resize", cols: 90, rows: 30, drive: true }), false)
+    );
+    assert.doesNotThrow(() => msg(a, "x", true));
+    ptys[1].__gone = true; // exited, onExit still queued
+    assert.doesNotThrow(() => msg(b, "y", true));
+  });
+
   it("kills the PTY attach process when the WS connection closes", () => {
     const ws = makeFakeWs();
     ptyAttach.attach(ws, "agenthub-lane-1", { cols: 80, rows: 24 });