fix(cli): wire command:result + system:reload socket events in TUI

Gateway slash command responses were silently dropped — use-socket.ts
had no handlers for command:result or system:reload. Added both:
- command:result → renders success/error as a system message
- system:reload → updates command registry manifest + shows reload message

Also removes stray @testing-library/react devDependency that was
never used in the CLI package.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/cli/src/tui/hooks/use-socket.ts

@@ -12,6 +12,8 @@ import type {
   SessionInfoPayload,
   ErrorPayload,
   CommandManifestPayload,
+  SlashCommandResultPayload,
+  SystemReloadPayload,
 } from '@mosaic/types';
 import { commandRegistry } from '../commands/index.js';
 
@@ -230,6 +232,27 @@ export function useSocket(opts: UseSocketOptions): UseSocketReturn {
       commandRegistry.updateManifest(data.manifest);
     });
 
+    socket.on('command:result', (data: SlashCommandResultPayload) => {
+      const prefix = data.success ? '' : 'Error: ';
+      const text = data.message ?? (data.success ? 'Done.' : 'Command failed.');
+      setMessages((msgs) => [
+        ...msgs,
+        { role: 'system', content: `${prefix}${text}`, timestamp: new Date() },
+      ]);
+    });
+
+    socket.on('system:reload', (data: SystemReloadPayload) => {
+      commandRegistry.updateManifest({
+        commands: data.commands,
+        skills: data.skills,
+        version: Date.now(),
+      });
+      setMessages((msgs) => [
+        ...msgs,
+        { role: 'system', content: data.message, timestamp: new Date() },
+      ]);
+    });
+
     return () => {
       socket.disconnect();
     };