[pinpols]

Summary

• Route frontend local and CI checks through shared gate controls and result formatting.
• Normalize mode/group output and report/ignore behavior; update docs and regression tests.
• Wrap remaining frontend CI and staging checks with the common gate runner.

Validation

• Frontend pre-commit and changed-file preflight passed.
• Gate result collection tests and shell checks passed.
• actionlint passed for frontend workflows.

Paired backend PR: pinpols/file-batch-system#1250