fix(anomaly-triage): parse documented metadata fields

[ArchonVII]

Summary

Fix anomaly-triage metadata parsing so the documented **Field:** value form retains severity, file, relatedness, and downstream-repo routing values. Keep the previously accepted **Field**: value form compatible.

Verification

• Executed the complete repository Vitest suite.

  command: npm test
  location: local
  result: Exit 0; 9 test files executed, 181 tests passed, 0 failed.
  timestamp: 2026-07-09T23:04:47-05:00
  

• Linted the changed reusable workflow.

  command: C:\Users\josep\go\bin\actionlint.exe .github\workflows\anomaly-triage.yml
  location: local
  result: Exit 0 with no findings.
  timestamp: 2026-07-09T23:04:48-05:00
  

• Checked the final committed patch for whitespace errors.

  command: git diff --check origin/main...HEAD
  location: local
  result: Exit 0; no whitespace errors.
  timestamp: 2026-07-09T23:05:30-05:00
  

Verification Notes

TDD RED: npx vitest run scripts/workflow-structure.test.mjs reported 1 failed / 22 passed before the parser change. TDD GREEN: the same command reported 23 passed after the parser change. The regression test reads the parser regular expression from the reusable workflow and exercises all four documented metadata fields plus the legacy colon placement.

The defect was observed in a live ArchonVII/sales proof: Related to PR: yes was discarded and routed as an unrelated issue.

Docs / Changelog

Added .changelog/unreleased/110-parse-anomaly-metadata.md and updated docs/repo-update-log.md.

Plan/status artifacts: not applicable because none were created or used by this lane.

Owner decisions this lane: none.

Linked Issue

Closes #110

Risks

• Risk level: low; the parser change is limited to metadata-field delimiter recognition.
• Rollback: revert commit 848bc4b and move the floating v1 tag back to the prior release commit if live routing regresses.
• Follow-ups: move v1 after merge and refresh the archon-setup reusable-workflow snapshot; consumer caller files do not change.