chore(config): drop unused plugin_system flags and a dead unit comment

- config.template.json: remove plugin_system.auto_discover,
  auto_load_enabled and development_mode. Nothing reads them; the web UI
  only stores them when a client sends them. ConfigManager's migration
  only adds template keys, so existing configs keep theirs unchanged.
- config.template.json: re-indent vegas_scroll's live_* keys.
- systemd/ledmatrix.service: remove the comment documenting
  LEDMATRIX_ON_DEMAND_PLUGIN / on_demand_env.conf; nothing reads either.
- CONFIG_REFERENCE.md: say the legacy keys are no longer in the template.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

config/config.template.json

@@ -133,9 +133,9 @@
         "plugin_rotation_order": [],
         "use_short_date_format": true,
         "vegas_scroll": {
-      "live_in_ticker": false,
-      "live_weight": 3,
-      "favorite_live_weight": 5,
+            "live_in_ticker": false,
+            "live_weight": 3,
+            "favorite_live_weight": 5,
             "enabled": false,
             "scroll_speed": 50,
             "separator_width": 32,
@@ -171,10 +171,7 @@
         "follower_position": "left"
     },
     "plugin_system": {
-        "plugins_directory": "plugin-repos",
-        "auto_discover": true,
-        "auto_load_enabled": true,
-        "development_mode": false
+        "plugins_directory": "plugin-repos"
     },
     "web-ui-info": {
         "enabled": true,

docs/CONFIG_REFERENCE.md

@@ -160,9 +160,7 @@ Read by `src/common/sync_manager.py` and `src/display_controller.py`.
 | Key | Type / default | Meaning |
 |---|---|---|
 | `plugins_directory` | string, `"plugin-repos"` | Where the Plugin Store installs plugins and the only directory the plugin loader scans. Read by `PluginManager` and `PluginStoreManager` (`src/plugin_system/`); editable under General settings |
-| `auto_discover` | bool, `true` | **Unused.** Legacy key, read by nothing. Plugins are always discovered, and every plugin with `enabled: true` is loaded. Not shown in the web UI; may be left in or removed from config.json |
-| `auto_load_enabled` | bool, `true` | **Unused.** Legacy key, read by nothing (see `auto_discover`). To keep a plugin installed but dormant, set its own `enabled` to `false` |
-| `development_mode` | bool, `false` | **Unused.** Legacy key, read by nothing |
+| `auto_discover`, `auto_load_enabled`, `development_mode` | bool | **Unused.** Legacy keys, read by nothing and no longer in the template; older configs may still carry them. Plugins are always discovered, and every plugin with `enabled: true` is loaded — to keep a plugin installed but dormant, set its own `enabled` to `false`. Not shown in the web UI; may be left in or removed from config.json |
 
 ## Plugin config blocks
 

systemd/ledmatrix.service

@@ -43,11 +43,6 @@ MemoryMax=85%
 StandardOutput=journal
 StandardError=journal
 SyslogIdentifier=ledmatrix
-# Support for on-demand plugin filtering via environment variable
-# The environment variable LEDMATRIX_ON_DEMAND_PLUGIN can be set via:
-# sudo systemctl set-environment LEDMATRIX_ON_DEMAND_PLUGIN=<plugin_id>
-# Or by using an EnvironmentFile (see below)
-# EnvironmentFile=__PROJECT_ROOT_DIR__/config/on_demand_env.conf
 
 [Install]
 WantedBy=multi-user.target