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/test_vegas_participation.py

@@ -434,28 +434,46 @@ class TestSchema:
 
 
 class TestInstalledPluginsApi:
+    """The web process runs no plugin code (it has a PluginCatalog, not a
+    PluginManager), so it reports what the files say -- the user's setting,
+    then the manifest -- and leaves the rest to the display."""
+
     @pytest.fixture
-    def installed(self, api_v3_module, api_v3_client, tmp_path):
-        def _get(instance, config):
+    def installed(self, api_v3_module, api_v3_client):
+        def _get(config, manifest_extra=None):
             api = api_v3_module.api_v3
-            info = {'id': 'demo', 'name': 'Demo', 'version': '1.0.0', 'loaded': True}
-            api.plugin_manager.plugins_dir = str(tmp_path)
-            api.plugin_manager.get_all_plugin_info = MagicMock(return_value=[info])
-            api.plugin_manager.get_plugin = MagicMock(return_value=instance)
+            info = {'id': 'demo', 'name': 'Demo', 'version': '1.0.0',
+                    **(manifest_extra or {})}
+            api.plugin_catalog.get_all_plugin_info = MagicMock(return_value=[info])
+            api.plugin_catalog.get_plugin_directory = MagicMock(return_value=None)
             api.plugin_store_manager.get_registry_info = MagicMock(return_value=None)
             api.config_manager.load_config = MagicMock(return_value={'demo': config})
             response = api_v3_client.get('/api/v3/plugins/installed')
             assert response.status_code == 200
-            return [p for p in response.get_json()['data']['plugins']
-                    if p['id'] == 'demo'][0]
+            entry = [p for p in response.get_json()['data']['plugins']
+                     if p['id'] == 'demo'][0]
+            return entry['vegas_participation'], entry['vegas_participation_source']
         return _get
 
-    def test_a_loaded_plugin_reports_its_participation(self, installed):
-        plugin = _plugin({'vegas_mode': 'static'})
-        assert installed(plugin, plugin.config)['vegas_participation'] == 'pause'
+    def test_the_user_setting_wins(self, installed):
+        assert installed({'vegas_participation': 'exclude'},
+                         {'vegas_participation': 'pause'}) == ('exclude', 'config')
 
-    def test_an_unloaded_plugin_reports_only_the_user_setting(self, installed):
-        assert installed(None, {'vegas_participation': 'exclude'})[
-            'vegas_participation'] == 'exclude'
-        assert installed(None, {})['vegas_participation'] is None
+    def test_then_the_manifest_declaration(self, installed):
+        assert installed({}, {'vegas_participation': 'Pause'}) == ('pause', 'manifest')
+        # An invalid setting is ignored, as the display ignores it.
+        assert installed({'vegas_participation': 'fixed'},
+                         {'vegas_participation': 'scroll'}) == ('scroll', 'manifest')
+
+    def test_otherwise_it_is_decided_at_run_time(self, installed):
+        # The legacy hooks would say 'pause' for vegas_mode 'static', but
+        # only the display runs them: nothing is guessed here.
+        assert installed({'vegas_mode': 'static'}) == (None, 'runtime')
+        assert installed({}, {'vegas_participation': 'sometimes'}) == (None, 'runtime')
+
+    def test_it_matches_the_display_where_the_files_decide(self, installed):
+        for config, manifest in (({'vegas_participation': 'pause'}, None),
+                                 ({}, {'vegas_participation': 'exclude'})):
+            plugin = _plugin(config, manifest)
+            assert installed(config, manifest)[0] == resolve_vegas_participation(plugin)