fix(plugins): web mode lookups use the modes the display registered (#668)

A plugin may compute its display modes from its config: soccer-scoreboard
registers soccer_<league>_live/recent/upcoming for every custom_leagues
entry, which no manifest can list ahead of time. The display always rotated
them (_register_loaded_plugin prefers plugin.modes), but the web process
reads plugins as files, so /display/modes, the on-demand dialog and
on-demand/start with a mode and no plugin_id saw only manifests -- a custom
league's mode was missing from every list and 404'd on lookup.

- PluginStateManager.record_modes(): the controller records what it
  registered, on the loaded record (an unload or reload forgets it)
- the runtime snapshot carries it per plugin as "modes" (bounded), and
  PluginRuntimeView.display_modes() reports it only while live
- PluginCatalog takes a runtime_source; get_plugin_display_modes and
  find_plugin_for_mode prefer the live modes, falling back to the manifest
  when the display is stopped or has not loaded the plugin. The view is read
  at most once a second, so a listing is one read, not one per plugin.

No manifest or plugin change needed.

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

src/display_controller.py

@@ -4617,6 +4617,15 @@ class DisplayController:
             display_modes = [plugin_id]
         with self._plugin_modes_lock:
             self.plugin_display_modes[plugin_id] = list(display_modes)
+        # Into the runtime snapshot the web interface reads, so its mode
+        # lists and on-demand lookups see computed modes too (#668).
+        state_manager = getattr(self.plugin_manager, 'state_manager', None)
+        record_modes = getattr(state_manager, 'record_modes', None)
+        if callable(record_modes):
+            try:
+                record_modes(plugin_id, list(display_modes))
+            except Exception as e:  # reporting must never break registration
+                logger.debug("Could not record display modes for %s: %s", plugin_id, e)
 
         # Subscribe to config changes for per-plugin hot-reload. Bind plugin_id
         # and instance as defaults so each plugin's callback targets its own