fix(metrics): Fix comment to say output generation instead of token counting

The overlap is between file metrics and output generation (await
outputPromise), not output token counting which starts only after
the output resolves.

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

Author: yamadashy

src/core/metrics/calculateSelectiveFileMetrics.ts

@@ -10,7 +10,7 @@ import type { FileMetrics } from './workers/types.js';
 // Each batch is sent as a single message to a worker thread, avoiding
 // per-file round-trip costs (~0.5ms each) that dominate when processing many files.
 // A size of 10 keeps individual worker tasks small so that workers become available sooner,
-// enabling overlap between file metrics and output token counting.
+// enabling overlap between file metrics and output generation.
 // When tokenCountTree is disabled, metrics only processes a small number of top files
 // (e.g., topFilesLength * 10 = 50 by default), so a smaller batch size avoids
 // a single batch monopolizing one worker.