fix(display): Vegas resumes after live priority, and six smaller runtime fixes (#644)

- Vegas: a live-priority pause was only lifted from inside run_frame(),
  which returns before that check while paused, so the ticker never came
  back until a restart. run_iteration() now resumes it (the controller
  only calls it when nothing preempts Vegas); start()/stop() clear the
  pause state. Iteration length is timed with the monotonic clock.
- Dim schedule: a per-day disabled day now updates the minute-gate cache,
  so brightness no longer flips back to dim within each minute.
- On-demand: a second request no longer overwrites the rotation resume
  index with the first request's mode.
- Render pipeline: reset() drops the prepared group and deferred queue,
  and a prefetch in flight across a reset discards its result.
- Sync: stop() removes the status file (and the controller's cleanup now
  calls it), standalone removes a stale one at startup, and writes use a
  unique mkstemp temp file.
- render_gate.swap_releases_gil() delegates to frame_timing.
- Stale docstrings/comments corrected.

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

test/test_render_gate.py

@@ -430,3 +430,25 @@ class TestVegasWiring:
         pipeline._prefetch_thread.join(5)
         assert seen == [(True, True)]
         assert pipeline._prepared_group == ["segment"]
+
+
+class TestBindingCheck:
+    """swap_releases_gil() is frame_timing's check, not a second copy of it."""
+
+    @pytest.mark.parametrize("contents, expected", [
+        (b"...PyEval_SaveThread...", True),
+        (b"stock binding", False),
+    ])
+    def test_agrees_with_frame_timing(self, monkeypatch, tmp_path, contents, expected):
+        from types import SimpleNamespace
+        from src.common import frame_timing
+        binding = tmp_path / "core.so"
+        binding.write_bytes(contents)
+        monkeypatch.setitem(sys.modules, "rgbmatrix.core",
+                            SimpleNamespace(__file__=str(binding)))
+        assert render_gate.swap_releases_gil() is expected
+        assert frame_timing.binding_releases_gil() is expected
+
+    def test_none_without_a_binding(self, monkeypatch):
+        monkeypatch.delitem(sys.modules, "rgbmatrix.core", raising=False)
+        assert render_gate.swap_releases_gil() is None