修复 Studio 失败测试并新增合并门禁

把丢失的 box 录像放回 apps/studio/tests/data/，修掉第 3 节 3–10 号与两处过时测试桩，
注册 timing 标记并让根目录收集零错误；新增 tools/gate.ps1 与可选的 pre-push 钩子。
验证：studio 524 通过 19 跳过、shared 467 通过 18 跳过、ui_check 632 项 0 失败、gate.ps1 退出码 0。
细节见 docs/test-repair-plan.zh.md。

apps/studio/tests/conftest.py

@@ -51,6 +51,14 @@ _TOOLS_DIR = Path(__file__).resolve().parents[1] / "tools"
 if _TOOLS_DIR.is_dir() and str(_TOOLS_DIR) not in sys.path:
     sys.path.insert(0, str(_TOOLS_DIR))
 
+# The tests' own directory, so ``_studio_helpers`` is importable however pytest was
+# started. Relying on pytest to insert it works only under the default import mode and
+# only for the directory a test file happens to sit in; naming it here is what lets the
+# suite be collected from the repository root (see ``docs/test-repair-plan.zh.md`` §4).
+_TESTS_DIR = Path(__file__).resolve().parent
+if str(_TESTS_DIR) not in sys.path:
+    sys.path.insert(0, str(_TESTS_DIR))
+
 
 @pytest.fixture(scope="session")
 def qt_app():
@@ -117,49 +125,6 @@ def decline_video_prompt(monkeypatch):
     )
 
 
-def visible_descendants(widget):
-    """Yield every visible descendant widget of ``widget``."""
-    for child in widget.findChildren(object):
-        if not hasattr(child, "isVisible") or not hasattr(child, "geometry"):
-            continue
-        if child.isVisible():
-            yield child
-
-
-def show_window(window, size):
-    """Show a window at ``size`` and flush pending Qt events."""
-    from PySide6.QtWidgets import QApplication
-
-    window.resize(*size)
-    window.show()
-    QApplication.processEvents()
-    return window
-
-
-def running_window(make_window):
-    """Return a running window backed by a controllable test worker."""
-    import ui_check
-
-    window = show_window(
-        make_window(sensor_type="box", source_mode="camera"),
-        (1440, 880),
-    )
-    stuck = ui_check._StuckWorker()
-    window._ensure_workers = lambda: None
-    window._box_worker = stuck
-    window._finger_worker = stuck
-    window._start_run()
-    window._run_timer.stop()
-    window._set_phase("running")
-    return window, stuck
-
-
-def finish_run(window, stuck):
-    """Stop a test run and release its controllable worker."""
-    window._stop_run(reason="user_stop")
-    stuck.release()
-
-
 _RECORD_SCRATCH = (
     Path(__file__).resolve().parents[1] / "outputs" / "_test_record"
 )