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/common/scroll_config.py

@@ -49,7 +49,7 @@ from __future__ import annotations
 
 import logging
 from dataclasses import dataclass, replace
-from typing import Any, Dict, Optional
+from typing import Any, Dict, List, Optional, cast
 
 from src.matrix_support import DEFAULT_REFRESH_LIMIT_HZ
 
@@ -132,14 +132,14 @@ def crisp_ladder(
     refresh_hz: float = DEFAULT_REFRESH_HZ,
     max_frame_hold: int = MAX_FRAME_HOLD,
     max_pixels_per_frame: int = MAX_PIXELS_PER_FRAME,
-):
+) -> List[CrispSpeed]:
     """Every whole-pixel speed this panel can show, slowest first.
 
     Duplicates are collapsed keeping the gentlest option: 100 px/s is reachable
     as 1px every refresh or 2px every 2nd refresh, and the former moves in
     smaller increments, so that is the one worth offering.
     """
-    best = {}
+    best: Dict[float, CrispSpeed] = {}
     for hold in range(1, max_frame_hold + 1):
         for ppf in range(1, max_pixels_per_frame + 1):
             pps = refresh_hz / hold * ppf
@@ -434,7 +434,8 @@ def configure(
     # they start scrolling. configure() only reports what is needed.
 
     if choice:
-        requested = settings.requested_pixels_per_second
+        # Set whenever there is a crisp choice (see the replace() above).
+        requested = cast(float, settings.requested_pixels_per_second)
         if abs(requested - applied) > 0.05:
             log.info(
                 "Scroll configured: %s (asked for %.1f px/s from %s; "