docs: refresh and correct stale documentation across repo

Walked the README and docs/ tree against current code and fixed several
real bugs and many stale references. Highlights:

User-facing
- README.md: web interface install instructions referenced
  install_web_service.sh at the repo root, but it actually lives at
  scripts/install/install_web_service.sh.
- docs/GETTING_STARTED.md: every web UI port reference said 5050, but
  the real server in web_interface/start.py:123 binds 5000. Same bug
  was duplicated in docs/TROUBLESHOOTING.md (17 occurrences). Fixed
  both.
- docs/GETTING_STARTED.md: rewrote tab-by-tab instructions. The doc
  referenced "Plugin Store", "Plugin Management", "Sports Configuration",
  "Durations", and "Font Management" tabs - none of which exist. Real
  tabs (verified in web_interface/templates/v3/base.html) are: Overview,
  General, WiFi, Schedule, Display, Config Editor, Fonts, Logs, Cache,
  Operation History, Plugin Manager (+ per-plugin tabs).
- docs/GETTING_STARTED.md: removed references to a "Test Display"
  button (doesn't exist) and "Show Now" / "Stop" plugin buttons. Real
  controls are "Run On-Demand" / "Stop On-Demand" inside each plugin's
  tab (partials/plugin_config.html:792).
- docs/TROUBLESHOOTING.md: removed dead reference to
  troubleshoot_weather.sh (doesn't exist anywhere in the repo); weather
  is now a plugin in ledmatrix-plugins.

Developer-facing
- docs/PLUGIN_API_REFERENCE.md: documented draw_image() doesn't exist
  on DisplayManager. Real plugins paste onto display_manager.image
  directly (verified in src/base_classes/{baseball,basketball,football,
  hockey}.py). Replaced with the canonical pattern.
- docs/PLUGIN_API_REFERENCE.md: documented cache_manager.delete() doesn't
  exist. Real method is clear_cache(key=None). Updated the section.
- docs/PLUGIN_API_REFERENCE.md: added 10 missing BasePlugin methods that
  the doc never mentioned: dynamic-duration hooks, live-priority hooks,
  and the full Vegas-mode interface.
- docs/PLUGIN_DEVELOPMENT_GUIDE.md: same draw_image fix.
- docs/DEVELOPMENT.md: corrected the "Plugin Submodules" section. Plugins
  are NOT git submodules - .gitmodules only contains
  rpi-rgb-led-matrix-master. Plugins are installed at runtime into the
  plugins directory configured by plugin_system.plugins_directory
  (default plugin-repos/). Both internal links in this doc were also
  broken (missing relative path adjustment).
- docs/HOW_TO_RUN_TESTS.md: removed pytest-timeout from install line
  (not in requirements.txt) and corrected the test/integration/ path
  (real integration tests are at test/web_interface/integration/).
  Replaced the fictional file structure diagram with the real one.
- docs/EMULATOR_SETUP_GUIDE.md: clone URL was a placeholder; default
  pixel_size was documented as 16 but emulator_config.json ships with 5.

Index
- docs/README.md: rewrote. Old index claimed "16-17 files after
  consolidation" but docs/ actually has 38 .md files. Four were missing
  from the index entirely (CONFIG_DEBUGGING, DEV_PREVIEW,
  PLUGIN_ERROR_HANDLING, STARLARK_APPS_GUIDE). Trimmed the navel-gazing
  consolidation/statistics sections.

Out of scope but worth flagging:
- src/plugin_system/resource_monitor.py:343 and src/common/api_helper.py:287
  call cache_manager.delete(key) but no such method exists on
  CacheManager. Both call sites would AttributeError at runtime if hit.
  Not fixed in this docs PR - either add a delete() shim or convert
  callers to clear_cache().

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/HOW_TO_RUN_TESTS.md

@@ -13,7 +13,7 @@ Make sure you have the testing packages installed:
 pip install -r requirements.txt
 
 # Or install just the test dependencies
-pip install pytest pytest-cov pytest-mock pytest-timeout
+pip install pytest pytest-cov pytest-mock
 ```
 
 ### 2. Set Environment Variables
@@ -85,8 +85,14 @@ pytest -m slow
 # Run all tests in the test directory
 pytest test/
 
-# Run all integration tests
-pytest test/integration/
+# Run plugin tests only
+pytest test/plugins/
+
+# Run web interface tests only
+pytest test/web_interface/
+
+# Run web interface integration tests
+pytest test/web_interface/integration/
 ```
 
 ## Understanding Test Output
@@ -231,20 +237,41 @@ pytest --maxfail=3
 
 ```
 test/
-├── conftest.py                    # Shared fixtures and configuration
-├── test_display_controller.py     # Display controller tests
-├── test_plugin_system.py          # Plugin system tests
-├── test_display_manager.py        # Display manager tests
-├── test_config_service.py         # Config service tests
-├── test_cache_manager.py          # Cache manager tests
-├── test_font_manager.py           # Font manager tests
-├── test_error_handling.py         # Error handling tests
-├── test_config_manager.py         # Config manager tests
-├── integration/                   # Integration tests
-│   ├── test_e2e.py               # End-to-end tests
-│   └── test_plugin_integration.py # Plugin integration tests
-├── test_error_scenarios.py        # Error scenario tests
-└── test_edge_cases.py             # Edge case tests
+├── conftest.py                          # Shared fixtures and configuration
+├── test_display_controller.py           # Display controller tests
+├── test_display_manager.py              # Display manager tests
+├── test_plugin_system.py                # Plugin system tests
+├── test_plugin_loader.py                # Plugin discovery/loading tests
+├── test_plugin_loading_failures.py      # Plugin failure-mode tests
+├── test_cache_manager.py                # Cache manager tests
+├── test_config_manager.py               # Config manager tests
+├── test_config_service.py               # Config service tests
+├── test_config_validation_edge_cases.py # Config edge cases
+├── test_font_manager.py                 # Font manager tests
+├── test_layout_manager.py               # Layout manager tests
+├── test_text_helper.py                  # Text helper tests
+├── test_error_handling.py               # Error handling tests
+├── test_error_aggregator.py             # Error aggregation tests
+├── test_schema_manager.py               # Schema manager tests
+├── test_web_api.py                      # Web API tests
+├── test_nba_*.py                        # NBA-specific test suites
+├── plugins/                             # Per-plugin test suites
+│   ├── test_clock_simple.py
+│   ├── test_calendar.py
+│   ├── test_basketball_scoreboard.py
+│   ├── test_soccer_scoreboard.py
+│   ├── test_odds_ticker.py
+│   ├── test_text_display.py
+│   ├── test_visual_rendering.py
+│   └── test_plugin_base.py
+└── web_interface/
+    ├── test_config_manager_atomic.py
+    ├── test_state_reconciliation.py
+    ├── test_plugin_operation_queue.py
+    ├── test_dedup_unique_arrays.py
+    └── integration/                     # Web interface integration tests
+        ├── test_config_flows.py
+        └── test_plugin_operations.py
 ```
 
 ### Test Categories