feat(ci): declare the trusted acceptance verifier registry [no-ticket]

[matthias-scale]

Summary

Revives the only undelivered content of #14: .github/acceptance-verifiers.json and its test.

#14 was a stale mixed branch. Its stated content — the Ghostty keyboard fix — is already on fork/pr-base (src/pane.rs sends \x1b[>5u\x1b[>4;2m…, src/main.rs uses ime_compatible_keyboard_enhancement_flags()), so nothing of the original author's work is lost by closing it. Its other QA files are older than base — checking them out would have deleted 159 lines of since-evolved script — so only the two genuinely new files are carried here.

What this does

Names check (ubuntu-latest) as herdr's trusted acceptance verifier, so /amerge can bind a Deep+ ci_surface to a named check rather than inferring one from the rollup.

Acceptance criteria

• ✓ Registry declares schema acceptance-verifiers/v1 and exactly one verifier — .github/acceptance-verifiers.json
• ✓ A workflow rename breaks the test instead of silently voiding the mapping — scripts/test_acceptance_verifier_registry.py asserts name: check (\${{ matrix.os }}), - os: ubuntu-latest, and the just ci run line in ci.yml
• ✓ Green — python3 -m pytest scripts/test_acceptance_verifier_registry.py -q → 1 passed

Validation

python3 -m pytest scripts/test_acceptance_verifier_registry.py -q
1 passed in 0.01s