e0e7929449
- single requirement checkbox + traceability table update
- mixed prefixes (TEST-XX, REG-XX, INFRA-XX) in single call
- space-separated ID input format
- bracket-wrapped [REQ-01, REQ-02] input format
- mixed valid/invalid IDs: valid updated, invalid in not_found
- idempotent: re-marking already-complete does not corrupt
- missing REQUIREMENTS.md returns {updated: false, reason: 'not found'}