[ExtraToast]

What

Adds the estate concurrency block to the workflows below that had none, or switches one that cancelled unconditionally to the guarded form:

concurrency:
  group: ${{ github.workflow }}-${{ github.ref }}
  cancel-in-progress: ${{ github.ref != 'refs/heads/main' }}

• .github/workflows/repository-hygiene.yml: added

Why

Every push to a pull request started a fresh run while the previous one, whose result nobody reads any more, kept its runner until it finished. Superseded runs now cancel as soon as a newer push lands. Runs on main are never cancelled mid-flight. This is the same block ~40 ci.yml files in the estate already carry.