fix: add --fast hint to /model description for discoverability (#3086)

Add "(--fast for suggestion model)" to the /model command description
so users can discover the feature from the command list, since --fast
completion no longer appears on empty input.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/cli/src/ui/commands/modelCommand.test.ts

@@ -33,7 +33,9 @@ describe('modelCommand', () => {
 
   it('should have the correct name and description', () => {
     expect(modelCommand.name).toBe('model');
-    expect(modelCommand.description).toBe('Switch the model for this session');
+    expect(modelCommand.description).toBe(
+      'Switch the model for this session (--fast for suggestion model)',
+    );
   });
 
   it('should return error when config is not available', async () => {

packages/cli/src/ui/commands/modelCommand.ts

@@ -17,7 +17,7 @@ import { getPersistScopeForModelSelection } from '../../config/modelProvidersSco
 export const modelCommand: SlashCommand = {
   name: 'model',
   get description() {
-    return t('Switch the model for this session');
+    return t('Switch the model for this session (--fast for suggestion model)');
   },
   kind: CommandKind.BUILT_IN,
   completion: async (_context, partialArg) => {