Audits an already-written use case (UC-XXX) or test case (TC-XXX) against its specification and reports a coverage matrix: which main success scenario steps, alternative flows, business rules, preconditions, and postconditions have code and tests behind them, which are still open, and which code or tests have drifted away from the specification. Use when the user asks to "check coverage", "run a coverage check", "is UC-001 fully implemented", "is UC-001 completely tested", "audit the use case", "show me the coverage matrix", "do a traceability check", "what is still missing for UC-001", or "can I set the status to Tested". This is specification coverage, not line coverage from a coverage report. It reports only — it writes no code, no tests, and no files. When the user wants the gaps closed rather than listed, use /implement, /implement-hilla, /browserless-test, /hilla-test, /karibu-test, or /playwright-test instead.