feat: add /enhance command to improve user prompts

This adds the /enhance command which uses an LLM to refine user prompts
based on conversation history.

Closes #25133

packages/cli/src/services/BuiltinCommandLoader.ts

@@ -31,6 +31,7 @@ import { corgiCommand } from '../ui/commands/corgiCommand.js';
 import { docsCommand } from '../ui/commands/docsCommand.js';
 import { directoryCommand } from '../ui/commands/directoryCommand.js';
 import { editorCommand } from '../ui/commands/editorCommand.js';
+import { enhanceCommand } from '../ui/commands/enhanceCommand.js';
 import { extensionsCommand } from '../ui/commands/extensionsCommand.js';
 import { footerCommand } from '../ui/commands/footerCommand.js';
 import { helpCommand } from '../ui/commands/helpCommand.js';
@@ -133,6 +134,7 @@ export class BuiltinCommandLoader implements ICommandLoader {
       docsCommand,
       directoryCommand,
       editorCommand,
+      enhanceCommand,
       ...(this.config?.getExtensionsEnabled() === false
         ? [
             {