* test(#1959): add failing-first SBFL contract + Ochiai correctness tests
Epic #1957 Phase 1B. Source-text-is-the-product contract tests (Ochiai
formula documented, Tarantula fallback, top-N seeding, no-coverage skip
logged, ranking->Evidence, Bohrbug gating) plus a behavioral Ochiai
formula-correctness section: bound [0,1], max-score invariant, a known-fault
fixture proving the fault ranks #1 (criterion 2), clean degradation on
zero failing tests, and two fast-check properties.
Failing-first: reference file and agent routing do not yet exist.
* feat(#1959): add spectrum-based fault localization (Ochiai) pre-filter to gsd-debugger
Epic #1957 Phase 1B. When a runnable test suite with per-test coverage exists
(>=1 failing AND >=1 passing test), the debugger computes an Ochiai
suspiciousness ranking over the coverage spectrum and seeds the top-N
suspicious locations into Evidence as first-class hypothesis candidates,
narrowing the search space deterministically before LLM reasoning. Tarantula
documented as fallback. Degrades cleanly (logged, never silent) when there is
no test suite, no failing tests, or no per-test coverage, and is explicitly
not trusted on flaky/Heisenbug spectra (pairs with Phase 2B bug-taxonomy).
Full rules extracted to gsd-core/references/debugger-sbfl.md (slim Phase 1.25
routing kept in the agent to respect the size cap). No new coverage framework
— reuses the project's existing test/coverage runner. INVENTORY + manifest +
agent-size baseline + install-parity goldens + AGENTS.md updated.
* test(#1959): bound property generators to valid coverage counts
The [0,1] property generated failedExec independently of totalFailed, but
Ochiai's score is only bounded by 1 under the coverage invariant
failedExec <= totalFailed (a failing test that executed s is one of the
totalFailed failing tests). Out-of-domain inputs (failedExec=100, totalFailed=5)
make the formula correctly return >1. Bound failedExec by totalFailed via
fc.chain so the property tests the real domain. Also cleaned up the ranking
property (removed dead code).
* fix(#1959): address orthogonal review (monotonicity property, degradation row, coverage bounding)
- Replace vacuous ranking property (true-by-sort-construction) with a
non-trivial monotonicity property: holding totalFailed + passedExec fixed,
ochiai is non-decreasing in failedExec. An inverted formula would fail it.
- Add the missing 'no passing tests' degradation row (preconditions require
>=1 passing test; Tarantula would divide by totalPassed=0).
- Bound the coverage subprocess (CLAUDE.md gauntlet): cap the coverage run,
degrade-to-skip on timeout, never hang the debug session.
- Reword 'discard the ranking' -> 'mark the Evidence entry as revoked (do not
delete)' per Kernighan auditability.
* test(#1959): bound monotonicity-property generator to valid coverage (failedExecA <= totalFailed)
* chore(#1959): backfill changeset pr number (PR #2403)
56a5c6404c