docs(code): document deliberate duplicates instead of merging them

The audit surfaced several near-duplicate implementations that turned
out to be either deliberate forks or behaviorally different — merging
any of them would risk changing behavior on installed devices, so each
now carries an explicit comment stating the relationship:

- VisualDisplayManager: headless fork of DisplayManager; header now
  lists the ~15 mirrored methods and warns that DisplayManager changes
  must be mirrored.
- normalize_abbreviation: LogoDownloader's version (called directly by
  nine scoreboard plugins) replaces filesystem-unsafe characters;
  LogoHelper's strips spaces. Logo filenames on existing installs
  depend on both behaviors staying put.
- The two PluginTestBase classes: the shipped one is plugin-author
  API, the repo's own richer harness lives in test/plugins/ — now
  cross-referenced.

Also verified (no change needed): ConfigManager's backup/rollback
methods genuinely delegate to AtomicConfigManager, and SportsCore
already delegates _read_bdf_native_size to FontManager.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SXb4mKcAkVaxkeTb3YnAdr

src/common/logo_helper.py

@@ -187,10 +187,17 @@ class LogoHelper:
     def normalize_abbreviation(self, team_abbr: str) -> str:
         """
         Normalize team abbreviation for consistent filename usage.
-        
+
+        NOTE: this deliberately differs from
+        LogoDownloader.normalize_abbreviation (src/logo_downloader.py),
+        which replaces filesystem-unsafe characters (/ \\ : * ? " < > |)
+        but does not strip spaces. Plugins call the LogoDownloader
+        version; changing either implementation changes which logo
+        filenames resolve on existing installs.
+
         Args:
             team_abbr: Raw team abbreviation
-            
+
         Returns:
             Normalized abbreviation
         """

src/logo_downloader.py

@@ -118,7 +118,14 @@ class LogoDownloader:
     
     @staticmethod
     def normalize_abbreviation(abbreviation: str) -> str:
-        """Normalize team abbreviation for consistent filename usage."""
+        """Normalize team abbreviation for consistent filename usage.
+
+        Public API: sports scoreboard plugins call this directly.
+        NOTE: LogoHelper.normalize_abbreviation (src/common/logo_helper.py)
+        is a deliberately different variant (strips spaces, fewer character
+        replacements) — keep both behaviors stable; logo filenames on
+        existing installs depend on them.
+        """
         # Handle special characters that can cause filesystem issues
         normalized = abbreviation.upper()
         

src/plugin_system/testing/plugin_test_base.py

@@ -2,6 +2,11 @@
 Base test class for LEDMatrix plugins.
 
 Provides common fixtures and helper methods for plugin testing.
+
+Note: this is the plugin-author-facing base class shipped with the
+core (importable as src.plugin_system.testing.plugin_test_base). The
+repo's own plugin tests use a separate, richer harness in
+test/plugins/test_plugin_base.py — the two are intentionally distinct.
 """
 
 import unittest

src/plugin_system/testing/visual_display_manager.py

@@ -10,6 +10,17 @@ without requiring hardware or the RGBMatrixEmulator. Used for:
 Unlike MockDisplayManager (which logs calls but doesn't render) or
 MagicMock (which tracks nothing visual), this class creates a real
 PIL Image canvas and draws text using the actual project fonts.
+
+MAINTENANCE WARNING: this class is a deliberate fork of
+src/display_manager.py so it can run without hardware. It mirrors
+these DisplayManager methods by name and behavior: _load_fonts,
+_draw_bdf_text, get_font_height, get_text_width, draw_text,
+draw_text_with_icons, draw_weather_icon (and the _draw_sun/_draw_cloud/
+_draw_rain/_draw_snow/_draw_storm family), format_date_with_ordinal,
+capture_mode, set_scrolling_state, is_currently_scrolling,
+process_deferred_updates, update_display, render_size. A behavior
+change to any of those in DisplayManager must be mirrored here, or
+plugin visual tests will pass against stale behavior.
 """
 
 import math