fix(cursor): tighten rate limit detection string matching

Use specific patterns ('rate limit', 'resource_exhausted', 'too many
requests') instead of broad 'rate' or 'limit' substrings that would
false-positive on unrelated errors like 'character limit exceeded'.

src/cursor/cursor-executor.ts

@@ -438,9 +438,11 @@ export class CursorExecutor {
 
       // Check for protobuf-decoded error
       if (result.error) {
+        const errorLower = result.error.toLowerCase();
         const isRateLimit =
-          result.error.toLowerCase().includes('rate') ||
+          errorLower.includes('rate limit') ||
-          result.error.toLowerCase().includes('limit');
+          errorLower.includes('resource_exhausted') ||
+          errorLower.includes('too many requests');
         yield {
           type: 'error',
           response: new Response(