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/plugin_system/plugin_executor.py

@@ -6,7 +6,7 @@ error isolation, and performance monitoring.
 """
 
 import time
-from typing import Any, Optional, Callable
+from typing import Any, Dict, Optional, Callable
 from threading import Thread
 import logging
 
@@ -62,7 +62,7 @@ class PluginExecutor:
         plugin_context = f"plugin {plugin_id}" if plugin_id else "plugin"
         
         # Use threading-based timeout (more reliable than signal-based)
-        result_container = {'value': None, 'exception': None, 'completed': False}
+        result_container: Dict[str, Any] = {'value': None, 'exception': None, 'completed': False}
         
         def target():
             try: