fix(gui): prevent TypeError in extension command registration and notification handling

- Add optional chaining for ext.manifest?.name with fallback to 'Unknown'
- Add null check for event.payload before destructuring
- Prevent 'Cannot read properties of undefined' errors in event handlers

AGENT1: Core & App Shell analysis and fixes

Author: factorydroid

cortex-gui/src/App.tsx

@@ -174,7 +174,7 @@ function ExtensionCommandRegistrar(): null {
       (ext.manifest?.contributes?.commands || []).map(contrib => ({
         id: contrib.command,
         label: contrib.title,
-        category: contrib.category || ext.manifest.name,
+        category: contrib.category || ext.manifest?.name || 'Unknown',
         action: () => extensions.executeExtensionCommand(contrib.command)
       }))
     );
@@ -198,7 +198,9 @@ function ExtensionNotificationListener(): null {
 
   onMount(async () => {
     unlisten = await listen("extension:notification", (event: any) => {
-      const { type, message } = event.payload;
+      const payload = event?.payload;
+      if (!payload) return;
+      const { type, message } = payload;
       if (type === "info") toast.info(message);
       else if (type === "error") toast.error(message);
     });

cortex-gui/src/AppCore.tsx

@@ -177,7 +177,7 @@ function ExtensionCommandRegistrar(): null {
       (ext.manifest?.contributes?.commands || []).map(contrib => ({
         id: contrib.command,
         label: contrib.title,
-        category: contrib.category || ext.manifest.name,
+        category: contrib.category || ext.manifest?.name || 'Unknown',
         action: () => extensions.executeExtensionCommand(contrib.command)
       }))
     );
@@ -201,7 +201,9 @@ function ExtensionNotificationListener(): null {
 
   onMount(async () => {
     unlisten = await listen("extension:notification", (event: any) => {
-      const { type, message } = event.payload;
+      const payload = event?.payload;
+      if (!payload) return;
+      const { type, message } = payload;
       if (type === "info") toast.info(message);
       else if (type === "error") toast.error(message);
     });