ci: mypy ratchet -- keep type-clean modules clean (71 modules, 536 -> 442 errors) (#661)

* ci: mypy ratchet -- keep type-clean modules clean

mypy-clean.txt lists the 71 modules under src/ that type-check clean;
scripts/check_types.py runs mypy (--follow-imports=silent) on exactly
those files and fails on any error or a missing/unsorted/duplicate entry.
A new "Type check (mypy ratchet)" CI job runs it with mypy 1.20.2 and
pinned stubs; the manual pre-commit mypy hook now runs the same script
(a local hook, so mypy sees the installed requirements like CI does).

35 modules were made clean with annotation-only fixes: hints, typing.cast,
TYPE_CHECKING imports, implicit-Optional defaults made explicit, and
annotations widened (never guards removed) where mypy called a defensive
isinstance check unreachable. No runtime behaviour change.

mypy.ini: numpy and orjson are treated as Any (follow_imports=skip, also
for stubs). numpy 2.3+ stubs use 3.12 `type` statements that mypy won't
parse at python_version 3.10, and orjson is optional, so seeing its stubs
made the result depend on whether it was installed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* chore: annotate check_types.py's list-form mypy subprocess

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

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

src/vegas_mode/stream_manager.py

@@ -14,7 +14,7 @@ Supports three display modes:
 import logging
 import threading
 import time
-from typing import Optional, List, Dict, Any, Deque, Tuple, TYPE_CHECKING
+from typing import Optional, List, Dict, Any, Deque, Tuple, TYPE_CHECKING, cast
 from collections import deque
 from dataclasses import dataclass, field
 from PIL import Image
@@ -698,7 +698,7 @@ class StreamManager:
         if plugin is None:
             return False
         try:
-            return plugin.get_vegas_display_mode() == VegasDisplayMode.STATIC
+            return cast(bool, plugin.get_vegas_display_mode() == VegasDisplayMode.STATIC)
         except Exception:
             logger.debug("[%s] get_vegas_display_mode() failed; treating as not STATIC",
                          plugin_id, exc_info=True)