fix(ipc): a plugin reload no longer freezes the panel during Vegas (#723)

A plugin.reload no longer freezes the panel during Vegas: the old instance is torn down and the new one loaded off the render thread (frame gap 3017 ms -> 9 ms in the ledpi reproduction). A failed or timed-out teardown stops the reload with a restart hint instead of loading over stale modules or tearing down an instance still in use.

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

src/vegas_mode/plugin_adapter.py

@@ -183,9 +183,27 @@ class PluginAdapter:
                     "round", plugin_id, self.PLUGIN_LOCK_TIMEOUT
                 )
                 return None
+            if not self._still_loaded(plugin, plugin_id):
+                return None
             return self._fetch_content(plugin, plugin_id, restricted=False,
                                        keyed=keyed)
 
+    def _still_loaded(self, plugin: 'BasePlugin', plugin_id: str) -> bool:
+        """Whether ``plugin`` is still the loaded instance of ``plugin_id``.
+
+        Checked once the plugin's lock is held: a reload or a disable can
+        take the instance out and tear it down while this fetch waited for
+        the lock (PluginManager.detach_plugin), and a torn-down instance is
+        not asked for content. True when the manager keeps no ``plugins``
+        mapping to ask.
+        """
+        plugins = getattr(self.plugin_manager, 'plugins', None)
+        if not isinstance(plugins, dict) or plugins.get(plugin_id) is plugin:
+            return True
+        logger.debug("[%s] Unloaded or reloaded while waiting for its lock; "
+                     "skipping the old instance", plugin_id)
+        return False
+
     def is_live_capable(self, plugin: 'BasePlugin', plugin_id: str) -> bool:
         """Whether to ask this plugin for live elements rather than pictures.
 
@@ -922,6 +940,8 @@ class PluginAdapter:
                 return None
             epochs = self.live_epochs
             epoch = epochs.get(plugin_id) if epochs is not None else 0
+            if not self._still_loaded(plugin, plugin_id):
+                return epoch, {}
             render_width = self.resolve_render_width(plugin, plugin_id)
             plugin._vegas_render_width = render_width
             try:

src/vegas_mode/stream_manager.py

@@ -333,8 +333,11 @@ class StreamManager:
         loaded = 0
 
         if hasattr(self.plugin_manager, 'plugins'):
-            loaded = len(self.plugin_manager.plugins)
-            for plugin_id, plugin in self.plugin_manager.plugins.items():
+            # A snapshot: a plugin reload adds and removes entries on its
+            # own thread (DisplayController._start_plugin_reload).
+            plugins = list(self.plugin_manager.plugins.items())
+            loaded = len(plugins)
+            for plugin_id, plugin in plugins:
                 if not getattr(plugin, 'enabled', False):
                     logger.debug("[%s] Vegas: skipped (not enabled)", plugin_id)
                     continue