## Description
Hardens two routine PR-review pain points from the recent open-PR sweep:
- PR Governance reruns could keep validating the stale
`pull_request_target` event body even after the live PR description had
been fixed.
- Main CI model-cache misses could surface as dozens of unrelated
memory-test failures instead of one clear cache-preflight failure.
This intentionally avoids PyPI/package-bloat and release/nightly
workflow changes so the PR stays scoped to review and CI stabilization.
## Type of Change
- [x] Bug fix
- [ ] New feature
- [ ] Documentation
- [x] Refactor
- [x] Tests only
## Changes Made
- Added `--body-file` support to `scripts/pr-governance.py` so workflows
can validate the current PR body rather than stale rerun payloads.
- Updated PR Governance to fetch the live PR body via the GitHub API
before validating template fields.
- Added a CI preflight script that loads the default
sentence-transformer model in offline mode and verifies the expected
embedding dimension.
- Wired that preflight into the sharded CI job before pytest starts,
turning missing/corrupt Hugging Face caches into one early, actionable
failure.
- Added workflow/script regression tests for the live-body override and
model-cache preflight placement.
## Testing
- [x] Unit tests
- [x] Lint/static checks
- [ ] Integration tests
- [ ] Manual testing
### Test Output
```text
uv run --with pytest --with pytest-asyncio python -m pytest scripts/tests/test_pr_governance.py scripts/tests/test_pr_health_workflow.py scripts/tests/test_ci_workflow.py -q
9 passed in 0.04s
uv run ruff check scripts/pr-governance.py scripts/ci/verify_hf_model_cache.py scripts/tests/test_pr_governance.py scripts/tests/test_pr_health_workflow.py scripts/tests/test_ci_workflow.py
All checks passed!
python -m py_compile scripts\ci\verify_hf_model_cache.py scripts\pr-governance.py
# passed
```
## Real Behavior Proof
- Environment: Windows 11, Python 3.13.3, isolated worktree
`C:\git\headroom\.worktrees\stabilization-hardening`.
- Exact command / steps: Ran the focused governance/workflow tests, ruff
on touched Python files, and `py_compile` for the executable scripts.
- Observed result: Governance tests prove a stale event body can be
overridden by the live PR body; workflow tests prove CI validates live
PR body and runs the Hugging Face offline-cache preflight before pytest
shards.
- Not tested: Full GitHub CI before PR creation; that will run on this
PR. The new Hugging Face preflight itself is intentionally not run
locally because it depends on the CI-warmed offline model cache.
## Review Readiness
- [x] I have performed a self-review
- [x] This PR is ready for human review
JD Davis
adb793bee1