fix: use verify mode for self-check CI workflow

The self-check workflow defaulted to drift mode, which requires an
ESLint config file that doesn't exist in this repo. Switch to verify
mode which only needs the instruction file and source directory.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: moonrunnerkc

.github/workflows/self-check.yml

@@ -13,7 +13,8 @@ jobs:
       - uses: actions/checkout@v4
       - uses: ./
         with:
+          mode: verify
           instruction-file: tests/fixtures/sample-claude.md
           output-dir: src
         env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}