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>

test/web_interface/test_plugin_widget_route.py

@@ -52,7 +52,7 @@ def make_client(tmp_path):
     """
     from web_interface.blueprints import pages_v3 as pv
 
-    original_pm = getattr(pv.pages_v3, "plugin_manager", None)
+    original_pm = getattr(pv.pages_v3, "plugin_catalog", None)
 
     def _build(plugins_dir=None, plugin_manager=_UNSET):
         base = PROJECT_ROOT / "web_interface"
@@ -64,7 +64,7 @@ def make_client(tmp_path):
         if plugin_manager is _UNSET:
             plugin_manager = MagicMock()
             plugin_manager.plugins_dir = str(plugins_dir or tmp_path)
-        pv.pages_v3.plugin_manager = plugin_manager
+        pv.pages_v3.plugin_catalog = plugin_manager
 
         app.register_blueprint(pv.pages_v3, url_prefix="")
         return app.test_client()
@@ -72,7 +72,7 @@ def make_client(tmp_path):
     try:
         yield _build
     finally:
-        pv.pages_v3.plugin_manager = original_pm
+        pv.pages_v3.plugin_catalog = original_pm
 
 
 URL = "/static/plugin-widgets/{}/{}.js"
@@ -211,7 +211,7 @@ def config_form(tmp_path):
     """Render a plugin's config partial with a temp plugin on disk."""
     from web_interface.blueprints import pages_v3 as pv
 
-    orig_pm = getattr(pv.pages_v3, "plugin_manager", None)
+    orig_pm = getattr(pv.pages_v3, "plugin_catalog", None)
     orig_cm = getattr(pv.pages_v3, "config_manager", None)
 
     def _render(plugin_id="soccer-scoreboard", schema=None, widgets=None,
@@ -226,8 +226,7 @@ def config_form(tmp_path):
         pm.get_plugin_info.return_value = {"id": plugin_id, "name": plugin_id}
         if version is not None:
             pm.get_plugin_info.return_value["version"] = version
-        pm.get_plugin.return_value = None
-        pv.pages_v3.plugin_manager = pm
+        pv.pages_v3.plugin_catalog = pm
 
         cm = MagicMock()
         cm.load_config.return_value = {plugin_id: {"enabled": True}}
@@ -244,7 +243,7 @@ def config_form(tmp_path):
     try:
         yield _render
     finally:
-        pv.pages_v3.plugin_manager = orig_pm
+        pv.pages_v3.plugin_catalog = orig_pm
         pv.pages_v3.config_manager = orig_cm