feat(OMN-10076): backfill_contracts script + impl

[jonahgabriel]

Summary

• Implements scripts/backfill_contracts.py for OMN-10076 (Task 14 of OMN-9582 contract auto-generation plan)
• Removes all 5 xfail markers from tests/unit/scripts/test_backfill_contracts.py; all tests now pass as regular unit tests

What the script does

• --range OMN-START:OMN-END (default OMN-123:OMN-9892) sweeps all ticket IDs in range
• Per ticket: skip if contracts/OMN-XXXX.yaml exists (idempotent), tombstone if Linear 404, generate skeleton via generate_skeleton_contract() if found
• --dry-run prints intended actions without writing
• Fails fast with nonzero exit + clear message when LINEAR_API_KEY is absent
• Reports: N generated, M skipped (exists), K tombstoned (not found), E errors

DoD evidence

• 5 unit tests pass: uv run pytest tests/unit/scripts/test_backfill_contracts.py -v → 5 passed
• Full suite: 1170 passed, 45 skipped, 0 failures
• uv run mypy src/ scripts/backfill_contracts.py --strict → Success: no issues
• uv run ruff format src/ scripts/ tests/ && uv run ruff check src/ scripts/ tests/ → All checks passed
• pre-commit run --all-files → all 22 hooks passed
• OMN-10061 trigger verified: git log --oneline origin/main | grep -q "OMN-10061" → exit 0

Scope

This PR implements the script only. Bulk execution across the full range is OMN-10073 (separate ticket), blocked on explicit trigger verification.

Related

• Parent: OMN-9582 (Contract Auto-Generation plan)
• Red tests PR: OMN-10075 (test(OMN-10075): red tests for backfill_contracts script #455, merged/queued)
• Dependency: OMN-10061 (dod_evidence patch for OMN-9829..9850, merged on main)

[skip-receipt-gate: OMN-10076 contract attached inline above]

[coderabbitai]

Warning

Rate limit exceeded

@jonahgabriel has exceeded the limit for the number of commits that can be reviewed per hour. Please wait 3 minutes and 59 seconds before requesting another review.

To keep reviews running without waiting, you can enable usage-based add-on for your organization. This allows additional reviews beyond the hourly cap. Account admins can enable it under billing.

⌛ How to resolve this issue?

After the wait time has elapsed, a review can be triggered using the @coderabbitai review command as a PR comment. Alternatively, push new commits to this PR.

We recommend that you space out your commits to avoid hitting the rate limit.

🚦 How do rate limits work?

CodeRabbit enforces hourly rate limits for each developer per organization.

Our paid plans have higher rate limits than the trial, open-source and free plans. In all cases, we re-allow further reviews after a brief timeout.

Please see our FAQ for further information.

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 282f96dd-55f2-4ae9-a1fc-3af75bf4c64e

📥 Commits

Reviewing files that changed from the base of the PR and between 91fd4cb and ab0b059.

📒 Files selected for processing (2)

• scripts/backfill_contracts.py
• tests/unit/scripts/test_backfill_contracts.py

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch jonah/omn-10076-backfill-impl

---

_{Comment @coderabbitai help to get the list of available commands and usage tips.}