feat(queue): server-side PTY-inject + idle-drained follow-up queue (W2)

The walk-away primitive: queue follow-up prompts and let a session advance itself
while you're gone — "run the tests" drains, and when Claude next goes idle "open a
PR" drains. Injection reuses writeInput (byte-identical to a keystroke, broadcasts
to all mirrored devices); the byte-shuttle is untouched.

- POST/GET/DELETE /live-sessions/:id/queue — POST/DELETE behind requireAllowedOrigin
  + a per-IP rate limit (QUEUE_RATE_MAX=20/min) + SESSION_ID_RE; text non-empty,
  byte-capped (QUEUE_ITEM_MAX_BYTES=4096, 16kb body), count-capped (QUEUE_MAX_ITEMS=10).
- Bounded per-session queue in manager (enqueueFollowup/drainOne/clearQueue);
  new optional queueLength on LiveSessionInfo.
- Idle drain: the Stop/SessionEnd /hook branch scheduleDrain()s a debounced timer
  (QUEUE_SETTLE_MS=1500). It drains exactly one entry only if the session still
  exists, hasn't exited, produced no output during settle, and is idle — three
  guards (debounced single timer + pop-one + settle re-check) → one entry per idle.
- New additive ServerMessage {type:'queue',length} broadcasts the count to mirrors
  (⧗N badge); FE enqueue via the quick-reply editor + TabApp.enqueueToActive.

Injected bytes go verbatim to the PTY (never built into a shell command). Verified
independently: typecheck + build:web clean, 1737 tests pass (real-PTY integration
covers idle-drain / one-per-idle / settle-guard). Foundation for templated launches,
auto-continue, and issue-intake (docs/ROADMAP.md).

test/manager.test.ts

@@ -88,6 +88,11 @@ const CFG: Config = {
   worktreeTimeoutMs: 10_000,
   defaultPermissionMode: 'default',
   allowAutoMode: false,
+  // W2 inject queue
+  queueEnabled: true,
+  queueMaxItems: 10,
+  queueItemMaxBytes: 4096,
+  queueSettleMs: 1500,
 };
 
 const DIMS: Dims = { cols: 80, rows: 24 };
@@ -1145,3 +1150,137 @@ describe('list — lastOutputAt field (T-iOS-37)', () => {
     });
   });
 });
+
+// ── W2: inject-queue methods (enqueueFollowup / drainOne / clearQueue) ────────
+describe('W2 inject queue — enqueueFollowup', () => {
+  it('appends and returns {ok,length}, broadcasting {type:queue,length} to clients', () => {
+    const mgr = createSessionManager(CFG);
+    nextPty = createMockPty();
+    const ws = createMockWs();
+    const s = mgr.handleAttach(ws, null, DIMS, 1_000);
+    ws.sent.length = 0;
+
+    const r1 = mgr.enqueueFollowup(s.meta.id, 'echo one\r');
+    expect(r1).toEqual({ ok: true, length: 1 });
+    expect(s.queue).toEqual(['echo one\r']);
+    expect(parseSent(ws).some((m) => m.type === 'queue' && m.length === 1)).toBe(true);
+
+    const r2 = mgr.enqueueFollowup(s.meta.id, 'echo two\r');
+    expect(r2).toEqual({ ok: true, length: 2 });
+    expect(s.queue).toEqual(['echo one\r', 'echo two\r']);
+  });
+
+  it('caps at queueMaxItems → {ok:false,reason:full}, no broadcast, queue unchanged', () => {
+    const mgr = createSessionManager({ ...CFG, queueMaxItems: 2 });
+    nextPty = createMockPty();
+    const ws = createMockWs();
+    const s = mgr.handleAttach(ws, null, DIMS, 1_000);
+    mgr.enqueueFollowup(s.meta.id, 'a');
+    mgr.enqueueFollowup(s.meta.id, 'b');
+    ws.sent.length = 0;
+
+    const r = mgr.enqueueFollowup(s.meta.id, 'c');
+    expect(r).toEqual({ ok: false, reason: 'full' });
+    expect(s.queue).toEqual(['a', 'b']); // immutable: unchanged
+    expect(parseSent(ws).some((m) => m.type === 'queue')).toBe(false); // no broadcast
+  });
+
+  it('unknown id → {ok:false,reason:unknown}', () => {
+    const mgr = createSessionManager(CFG);
+    expect(mgr.enqueueFollowup('11111111-1111-4111-8111-111111111111', 'x')).toEqual({
+      ok: false,
+      reason: 'unknown',
+    });
+  });
+
+  it('exited session → {ok:false,reason:exited}', () => {
+    const mgr = createSessionManager(CFG);
+    nextPty = createMockPty();
+    const s = mgr.handleAttach(createMockWs(), null, DIMS, 1_000);
+    s.exitedAt = 2_000;
+    expect(mgr.enqueueFollowup(s.meta.id, 'x')).toEqual({ ok: false, reason: 'exited' });
+  });
+});
+
+describe('W2 inject queue — drainOne', () => {
+  it('pops the head, writes it to the PTY, shrinks the queue, and broadcasts depth', () => {
+    const mgr = createSessionManager(CFG);
+    nextPty = createMockPty();
+    const ws = createMockWs();
+    const s = mgr.handleAttach(ws, null, DIMS, 1_000);
+    mgr.enqueueFollowup(s.meta.id, 'HEAD\r');
+    mgr.enqueueFollowup(s.meta.id, 'TAIL\r');
+    ws.sent.length = 0;
+    const pty = s.pty as MockIPty;
+    pty.writes.length = 0;
+
+    const drained = mgr.drainOne(s.meta.id);
+    expect(drained).toBe('HEAD\r');
+    expect(pty.writes).toEqual(['HEAD\r']); // byte-identical inject
+    expect(s.queue).toEqual(['TAIL\r']); // length now 1
+    expect(parseSent(ws).some((m) => m.type === 'queue' && m.length === 1)).toBe(true);
+  });
+
+  it('empty queue → null, no PTY write', () => {
+    const mgr = createSessionManager(CFG);
+    nextPty = createMockPty();
+    const s = mgr.handleAttach(createMockWs(), null, DIMS, 1_000);
+    const pty = s.pty as MockIPty;
+    pty.writes.length = 0;
+
+    expect(mgr.drainOne(s.meta.id)).toBeNull();
+    expect(pty.writes).toEqual([]);
+  });
+
+  it('exited session with items queued → null (double-guards L4), no write', () => {
+    const mgr = createSessionManager(CFG);
+    nextPty = createMockPty();
+    const s = mgr.handleAttach(createMockWs(), null, DIMS, 1_000);
+    mgr.enqueueFollowup(s.meta.id, 'x');
+    s.exitedAt = 2_000;
+    const pty = s.pty as MockIPty;
+    pty.writes.length = 0;
+
+    expect(mgr.drainOne(s.meta.id)).toBeNull();
+    expect(pty.writes).toEqual([]);
+  });
+
+  it('unknown id → null', () => {
+    const mgr = createSessionManager(CFG);
+    expect(mgr.drainOne('11111111-1111-4111-8111-111111111111')).toBeNull();
+  });
+});
+
+describe('W2 inject queue — clearQueue', () => {
+  it('empties the queue, broadcasts length 0, returns true', () => {
+    const mgr = createSessionManager(CFG);
+    nextPty = createMockPty();
+    const ws = createMockWs();
+    const s = mgr.handleAttach(ws, null, DIMS, 1_000);
+    mgr.enqueueFollowup(s.meta.id, 'a');
+    mgr.enqueueFollowup(s.meta.id, 'b');
+    ws.sent.length = 0;
+
+    expect(mgr.clearQueue(s.meta.id)).toBe(true);
+    expect(s.queue).toEqual([]);
+    expect(parseSent(ws).some((m) => m.type === 'queue' && m.length === 0)).toBe(true);
+  });
+
+  it('unknown id → false', () => {
+    const mgr = createSessionManager(CFG);
+    expect(mgr.clearQueue('11111111-1111-4111-8111-111111111111')).toBe(false);
+  });
+});
+
+describe('W2 inject queue — list() surfaces queueLength', () => {
+  it('reports the pending depth per session', () => {
+    const mgr = createSessionManager(CFG);
+    nextPty = createMockPty();
+    const s = mgr.handleAttach(createMockWs(), null, DIMS, 1_000);
+    mgr.enqueueFollowup(s.meta.id, 'a');
+    mgr.enqueueFollowup(s.meta.id, 'b');
+
+    const entry = mgr.list().find((e) => e.id === s.meta.id);
+    expect(entry?.queueLength).toBe(2);
+  });
+});