docs: fix misc remaining docs (architecture, dev quickref, sub-dir READMEs)

PLUGIN_ARCHITECTURE_SPEC.md
- Added a banner at the top noting this is a historical design doc
  written before the plugin system shipped. The doc is ~1900 lines
  with 13 stale /api/plugins/* paths (real is /api/v3/plugins/*),
  references to web_interface_v2.py (current is app.py), and a
  Migration Strategy / Implementation Roadmap that's now history.
  Banner points readers at the current docs
  (PLUGIN_DEVELOPMENT_GUIDE, PLUGIN_API_REFERENCE,
  REST_API_REFERENCE) without needing to retrofit every section.

PLUGIN_CONFIG_ARCHITECTURE.md
- 10 occurrences of /api/plugins/* missing /v3 prefix. Bulk fixed.

DEVELOPER_QUICK_REFERENCE.md
- cache_manager.delete("key") -> cache_manager.clear_cache("key")
  with comment noting delete() doesn't exist. Same bug already
  documented in PLUGIN_API_REFERENCE.md.

SSH_UNAVAILABLE_AFTER_INSTALL.md
- 4 occurrences of port 5001 -> 5000 in AP-mode and Ethernet/WiFi
  recovery instructions.

PLUGIN_CUSTOM_ICONS_FEATURE.md
- Port 5001 -> 5000.

CONFIG_DEBUGGING.md
- Documented /api/v3/config/plugin/<id> and /api/v3/config/validate
  endpoints don't exist. Replaced with the real endpoints:
  /api/v3/config/main, /api/v3/plugins/schema?plugin_id=,
  /api/v3/plugins/config?plugin_id=. Added a note that validation
  runs server-side automatically on POST.

STARLARK_APPS_GUIDE.md
- "Plugins -> Starlark Apps" UI navigation path doesn't exist (5
  occurrences). Replaced with the real path: Plugin Manager tab,
  then the per-plugin Starlark Apps tab in the second nav row.
- "Navigate to Plugins" install step -> Plugin Manager tab.

web_interface/README.md
- Documented several endpoints that don't exist in the api_v3
  blueprint:
  - GET /api/v3/plugins (list) -> /api/v3/plugins/installed
  - GET /api/v3/plugins/<id> -> doesn't exist
  - POST /api/v3/plugins/<id>/config -> POST /api/v3/plugins/config
  - GET /api/v3/plugins/<id>/enable + /disable -> POST /api/v3/plugins/toggle
  - GET /api/v3/store/plugins -> /api/v3/plugins/store/list
  - POST /api/v3/store/install/<id> -> POST /api/v3/plugins/install
  - POST /api/v3/store/uninstall/<id> -> POST /api/v3/plugins/uninstall
  - POST /api/v3/store/update/<id> -> POST /api/v3/plugins/update
  - POST /api/v3/display/start/stop/restart -> POST /api/v3/system/action
  - GET /api/v3/display/status -> GET /api/v3/system/status
- Also fixed config/secrets.json -> config/config_secrets.json
- Replaced the per-section endpoint duplication with a current real
  endpoint list and a pointer to docs/REST_API_REFERENCE.md.
- Documented that SSE stream endpoints are defined directly on the
  Flask app at app.py:607-615, not in the api_v3 blueprint.

scripts/install/README.md
- Was missing 3 of the 9 install scripts in the directory:
  one-shot-install.sh, configure_wifi_permissions.sh, and
  debug_install.sh. Added them with brief descriptions.

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

web_interface/README.md

@@ -66,38 +66,50 @@ Once running, access the web interface at:
 
 The web interface reads configuration from:
 - `config/config.json` - Main configuration
-- `config/secrets.json` - API keys and secrets
+- `config/config_secrets.json` - API keys and secrets
 
 ## API Documentation
 
-The V3 API is available at `/api/v3/` with the following endpoints:
+The V3 API is mounted at `/api/v3/` (`app.py:144`). For the complete
+list and request/response formats, see
+[`docs/REST_API_REFERENCE.md`](../docs/REST_API_REFERENCE.md). Quick
+reference for the most common endpoints:
 
 ### Configuration
 - `GET /api/v3/config/main` - Get main configuration
 - `POST /api/v3/config/main` - Save main configuration
 - `GET /api/v3/config/secrets` - Get secrets configuration
-- `POST /api/v3/config/secrets` - Save secrets configuration
+- `POST /api/v3/config/raw/main` - Save raw main config (Config Editor)
+- `POST /api/v3/config/raw/secrets` - Save raw secrets
 
-### Display Control
-- `POST /api/v3/display/start` - Start display service
-- `POST /api/v3/display/stop` - Stop display service
-- `POST /api/v3/display/restart` - Restart display service
-- `GET /api/v3/display/status` - Get display service status
+### Display & System Control
+- `GET /api/v3/system/status` - System status
+- `POST /api/v3/system/action` - Control display (action body:
+  `start_display`, `stop_display`, `restart_display_service`,
+  `restart_web_service`, `git_pull`, `reboot_system`, `shutdown_system`)
+- `GET /api/v3/display/current` - Current display frame
+- `GET /api/v3/display/on-demand/status` - On-demand status
+- `POST /api/v3/display/on-demand/start` - Trigger on-demand display
+- `POST /api/v3/display/on-demand/stop` - Clear on-demand
 
 ### Plugins
-- `GET /api/v3/plugins` - List installed plugins
-- `GET /api/v3/plugins/<id>` - Get plugin details
-- `POST /api/v3/plugins/<id>/config` - Update plugin configuration
-- `GET /api/v3/plugins/<id>/enable` - Enable plugin
-- `GET /api/v3/plugins/<id>/disable` - Disable plugin
+- `GET /api/v3/plugins/installed` - List installed plugins
+- `GET /api/v3/plugins/config?plugin_id=<id>` - Get plugin config
+- `POST /api/v3/plugins/config` - Update plugin configuration
+- `GET /api/v3/plugins/schema?plugin_id=<id>` - Get plugin schema
+- `POST /api/v3/plugins/toggle` - Enable/disable plugin
+- `POST /api/v3/plugins/install` - Install from registry
+- `POST /api/v3/plugins/install-from-url` - Install from GitHub URL
+- `POST /api/v3/plugins/uninstall` - Uninstall plugin
+- `POST /api/v3/plugins/update` - Update plugin
 
 ### Plugin Store
-- `GET /api/v3/store/plugins` - List available plugins
-- `POST /api/v3/store/install/<id>` - Install plugin
-- `POST /api/v3/store/uninstall/<id>` - Uninstall plugin
-- `POST /api/v3/store/update/<id>` - Update plugin
+- `GET /api/v3/plugins/store/list` - List available registry plugins
+- `POST /api/v3/plugins/store/refresh` - Refresh registry from GitHub
 
 ### Real-time Streams (SSE)
+SSE stream endpoints are defined directly on the Flask app
+(`app.py:607-615`), not on the api_v3 blueprint:
 - `GET /api/v3/stream/stats` - System statistics stream
 - `GET /api/v3/stream/display` - Display preview stream
 - `GET /api/v3/stream/logs` - Service logs stream