fix(display): thread-safety for deferred updates, BDF faces and follower image; one refresh default (#652)

- DisplayManager.defer_update()/process_deferred_updates(): one lock around
  every queue mutation (appends from the update thread were lost to the
  render thread's filter/slice reassignments); callables run outside it.
- FontManager and element_style no longer cache BDF freetype.Face objects
  process-wide (load_bdf_face caches them per thread); element_style's LRU
  is locked against get/move_to_end vs eviction races.
- limit_refresh_rate_hz default is one constant, DEFAULT_REFRESH_LIMIT_HZ =
  100 (the template's), for the library options, refresh_hz, the matrix
  guard, Vegas and scroll_config. Previously a missing key capped the panel
  at 90 while pacing assumed 100.
- Sync follower: the TCP thread queues the leader's scroll image; the render
  thread swaps image/array/width in between frames.
- update_display() error log rate-limited (traceback first, then once a
  minute with a count); swallowed DisplayController exceptions log at DEBUG.
- Root display_controller.py runs run.py via runpy.
- stream_manager: correct the RLock release comments; merge duplicate if.

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

src/common/scroll_config.py

@@ -51,6 +51,8 @@ import logging
 from dataclasses import dataclass, replace
 from typing import Any, Dict, Optional
 
+from src.matrix_support import DEFAULT_REFRESH_LIMIT_HZ
+
 logger = logging.getLogger(__name__)
 
 #: Speed used when a plugin supplies nothing usable. One pixel per refresh on a
@@ -63,8 +65,9 @@ MIN_PIXELS_PER_SECOND = 1.0
 MAX_PIXELS_PER_SECOND = 500.0
 
 #: Assumed refresh when the caller does not say. Matches the usual
-#: ``display.hardware.limit_refresh_rate_hz``.
-DEFAULT_REFRESH_HZ = 100.0
+#: ``display.hardware.limit_refresh_rate_hz``, and is the cap DisplayManager
+#: applies when that key is missing.
+DEFAULT_REFRESH_HZ = float(DEFAULT_REFRESH_LIMIT_HZ)
 
 #: How far px/s may sit from a whole number of pixels per refresh before it is
 #: worth warning about. 0.05px per frame is invisible; a third of a pixel is not.