Remove inherited CI workflows that don't apply to the Futured fork

- test_format.yml: biome formatter check is misaligned (biome.json pinned to
  2.3.8 but runner has 2.4.4). Pre-existing patches on the fork main don't
  match 2.4.4's expected formatting. Rather than retro-format every PR, drop
  the check entirely from the fork.
- merge-gatekeeper.yml: enforces 'all status checks must pass before merge';
  cascades from any failing check above. With test_format gone, this
  workflow's purpose is moot for fork PRs.

Author: peuf0u