Merge branch 'tool-windows'

Add tool windows: tool registry, styled aux tmux windows
(TmuxRunner.new_aux_window / TmuxManager.open_aux_window),
SessionService tool-window + clone-for-window methods, and
hqt tool / hqt palette CLI subcommands (fzf tool launcher).

# Conflicts:
#	src/hqt/cli.py
#	src/hqt/tmux/manager.py
#	tests/test_cli.py
#	tests/test_sessions.py

tests/test_sessions.py

@@ -2010,3 +2010,121 @@ async def test_sandboxed_worktree_binds_repo_git_dir(
         )
     binds = mock_wrap.call_args.args[3]
     assert Bind(Path("/tmp/myproj/.git"), writable=True) in binds
+
+
+# ---------------------------------------------------------------------------
+# Task 4: SessionService tool-window methods
+# ---------------------------------------------------------------------------
+
+
+@pytest.mark.asyncio
+async def test_open_tool_window_spawns_styled_window(service, db, tmux, monkeypatch):
+    await service.create_session(project_id=1, harness_name="claude-code")
+    monkeypatch.setattr("hqt.sessions.service.shutil.which", lambda b: "/usr/bin/" + b)
+    tmux.open_aux_window = AsyncMock(return_value="@5")
+
+    wid = await service.open_tool_window(1, "lazygit")
+
+    assert wid == "@5"
+    tmux.open_aux_window.assert_awaited_once_with(
+        "lazygit", "/tmp/myproj", ["lazygit"], "lazygit · myproj"
+    )
+
+
+@pytest.mark.asyncio
+async def test_open_tool_window_shell_skips_which_check(service, db, tmux, monkeypatch):
+    await service.create_session(project_id=1, harness_name="claude-code")
+    monkeypatch.setattr("hqt.sessions.service.shutil.which", lambda b: None)
+    tmux.open_aux_window = AsyncMock(return_value="@3")
+
+    wid = await service.open_tool_window(1, "shell")
+
+    assert wid == "@3"
+    tmux.open_aux_window.assert_awaited_once_with(
+        "shell", "/tmp/myproj", [], "shell · myproj"
+    )
+
+
+@pytest.mark.asyncio
+async def test_open_tool_window_unknown_tool_raises(service):
+    with pytest.raises(ServiceError):
+        await service.open_tool_window(1, "emacs")
+
+
+@pytest.mark.asyncio
+async def test_open_tool_window_missing_binary_raises(service, db, monkeypatch):
+    await service.create_session(project_id=1, harness_name="claude-code")
+    monkeypatch.setattr("hqt.sessions.service.shutil.which", lambda b: None)
+    with pytest.raises(ServiceError):
+        await service.open_tool_window(1, "lazygit")
+
+
+@pytest.mark.asyncio
+async def test_open_tool_window_unknown_session_raises(service, monkeypatch):
+    monkeypatch.setattr("hqt.sessions.service.shutil.which", lambda b: "/usr/bin/" + b)
+    with pytest.raises(ServiceError):
+        await service.open_tool_window(999, "nvim")
+
+
+@pytest.mark.asyncio
+async def test_session_id_for_window_resolves_and_misses(service, db):
+    await service.create_session(project_id=1, harness_name="claude-code")
+    assert service.session_id_for_window("hqt-1") == 1
+    assert service.session_id_for_window("not-an-hqt-window") is None
+
+
+@pytest.mark.asyncio
+async def test_open_tool_window_for_window_resolves_by_name(
+    service, db, tmux, monkeypatch
+):
+    await service.create_session(project_id=1, harness_name="claude-code")
+    monkeypatch.setattr("hqt.sessions.service.shutil.which", lambda b: "/usr/bin/" + b)
+    tmux.open_aux_window = AsyncMock(return_value="@2")
+
+    wid = await service.open_tool_window_for_window("hqt-1", "nvim")
+
+    assert wid == "@2"
+    tmux.open_aux_window.assert_awaited_once_with(
+        "nvim", "/tmp/myproj", ["nvim"], "nvim · myproj"
+    )
+
+
+@pytest.mark.asyncio
+async def test_open_tool_window_for_window_unknown_window_raises(service):
+    with pytest.raises(ServiceError):
+        await service.open_tool_window_for_window("not-an-hqt-window", "nvim")
+
+
+# ---------------------------------------------------------------------------
+# Task 5: clone_session_for_window
+# ---------------------------------------------------------------------------
+
+
+@pytest.mark.asyncio
+async def test_clone_session_for_window_reuses_project_harness_model(
+    service, db, monkeypatch
+):
+    await service.create_session(
+        project_id=1, harness_name="claude-code", nickname="orig", model="opus"
+    )
+    captured = {}
+
+    async def fake_create(
+        project_id, harness_name, nickname=None, model=None, worktree_branch=None
+    ):
+        captured["args"] = (project_id, harness_name, nickname, model)
+        return "SENTINEL"
+
+    monkeypatch.setattr(service, "create_session", fake_create)
+
+    result = await service.clone_session_for_window("hqt-1")
+
+    assert result == "SENTINEL"
+    # Same project + harness + model; a fresh sibling, so no nickname.
+    assert captured["args"] == (1, "claude-code", None, "opus")
+
+
+@pytest.mark.asyncio
+async def test_clone_session_for_window_unknown_window_raises(service):
+    with pytest.raises(ServiceError):
+        await service.clone_session_for_window("not-an-hqt-window")