refactor(web): read plugins through a PluginCatalog; only the display runs them (#688)

The web process built its own PluginManager and loaded plugins into itself:
store installs and updates loaded or reloaded a web-side copy, and config
saves and enable/disable called on_config_change, on_enable and on_disable
on it. None of that reached the panel, and /plugins/installed reported
runtime state from those copies.

- Add PluginCatalog (src/plugin_system/plugin_catalog.py): manifests,
  directories, display modes, installed version, schema and config reads,
  with no way to run a plugin. app.py and both blueprints use it; the
  plugin_manager blueprint attribute is gone.
- Remove every lifecycle call from the web routes. Config changes already
  reach the display through ConfigService (on_config_change) and the
  enabled-set reconcile.
- Health and metrics readers move to api_v3.health_tracker /
  resource_monitor. /plugins/installed reports loaded/state/error_info as
  null (the display does not publish them) and enabled by the display's
  rule.
- Store install, update and uninstall answer restart_required when the
  running display will not pick the change up by itself
  (display_restart_required). The restart banner follows the flag via
  window.noteRestartRequired instead of the /config/main URL heuristic;
  /config/main now sends restart_required: true.
- The one remaining in-process import of plugin code (Starlark helper
  modules, oauth_flow action scripts) goes through
  _import_plugin_code_in_web_process() until a web-entry contract.
- /plugins/installed reports vegas_participation (from #682) from the
  user's setting or the manifest, with vegas_participation_source; when
  only the plugin's code decides it, null with source 'runtime', since the
  web process no longer has plugin instances to ask.
- Check & Update All keeps its restart flags when the final list refresh
  fails, and asks for a restart when an enabled plugin's first request got
  no answer and the re-sent one found it up to date.

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

web_interface/blueprints/api_v3/plugin_operations.py

@@ -120,10 +120,10 @@ def get_plugin_state():
 def reconcile_plugin_state():
     """Reconcile plugin state across all sources"""
     try:
-        if not api_v3.plugin_state_manager or not api_v3.plugin_manager:
+        if not api_v3.plugin_state_manager or not api_v3.plugin_catalog:
             return error_response(
                 ErrorCode.SYSTEM_ERROR,
-                'State manager or plugin manager not initialized',
+                'State manager or plugin catalog not initialized',
                 status_code=500
             )
 
@@ -139,8 +139,8 @@ def reconcile_plugin_state():
         reconciler = StateReconciliation(
             state_manager=api_v3.plugin_state_manager,
             config_manager=api_v3.config_manager,
-            plugin_manager=api_v3.plugin_manager,
-            plugins_dir=Path(api_v3.plugin_manager.plugins_dir)
+            plugin_manager=api_v3.plugin_catalog,
+            plugins_dir=Path(api_v3.plugin_catalog.plugins_dir)
         )
 
         result = reconciler.reconcile_state(force=force)
@@ -205,7 +205,7 @@ def _drop_stale_reconciliation_findings(unresolved):
         )
 
         cm = api_v3.config_manager
-        plugins_dir = getattr(api_v3.plugin_manager, 'plugins_dir', None)
+        plugins_dir = getattr(api_v3.plugin_catalog, 'plugins_dir', None)
         installed = disk_plugin_ids(plugins_dir) if plugins_dir else set()
         config_keys = config_plugin_ids(cm.load_config() or {},
                                        ignored_config_keys(cm, installed))