fix(cli): revert tools:[] to empty config for provider compatibility

Revert tools:[] to empty config {} to avoid provider compatibility
issues. Empty tools array is truthy and gets passed through to API
requests, which can cause errors on some providers. Omitting the
tools field entirely achieves the same effect (no tool access).

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

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

@@ -171,7 +171,7 @@ describe('btwCommand', () => {
             ],
           },
         ],
-        { tools: [] },
+        {},
         expect.any(AbortSignal),
         'test-model',
       );

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

@@ -45,7 +45,7 @@ async function askBtw(
         ],
       },
     ],
-    { tools: [] },
+    {}, // No tools — btw questions are text-only
     abortSignal,
     model,
   );