fix(1259-01): close adversarial review findings — genuine enforcement, honest fail-first scope

Adversarial pre-submission review found the injected-runCheck tests masked a
non-functional real runner. Fixes:

- BL-01 (false green on vacuous test): the node-test runner now parses the TAP
  summary and requires a NON-VACUOUS pass (>=1 test, >=1 pass, 0 fail) AND a
  reported test named distinctly from the file — node --test counts an empty file
  as one passing test, so counts alone could not catch it.
- SF-01 (lint anchor never greened): the lint-rule runner now runs the project
  eslint as --format json and filters by ruleId, so plugin rules (local/*) load
  via the flat config — bare --rule cannot load a plugin. local/no-source-grep
  now genuinely greens (covered by a real, non-injected test).
- BL-02 (tautological fail-first): the runner no longer echoes the caller's
  failFirst as if confirmed. failFirst is documented as caller-ATTESTED; the
  producer requires attestation + a genuine non-vacuous pass. Machine-proven
  fail-first (needs a violation fixture) is flagged as a tracked follow-up in
  ADR-550, the changeset, FEATURES, the reference doc, and verify-phase.
- SF-02: added real-runner end-to-end tests (no injected runCheck) + pure,
  exported parse/filter helpers (parseNodeTestSummary, tapTestNames,
  eslintJsonHasRule, eslintFileResultCount) so the shipping branches are
  mutation-pinned.
- NIT-01/02: LOCATE guard rejects empty-string rule and unknown kinds.
- Hardening: spawn checks with NODE_TEST_CONTEXT/NODE_OPTIONS scrubbed so an
  ambient test-runner context cannot corrupt a verify-time result.
- Docs reconciled to the shipped behavior (no 'confirms fail-first' overclaim).

.changeset/1259-test-tier-enforcement.md

@@ -3,6 +3,8 @@ type: Changed
 pr: 1259
 ---
 
-**Test-tier prohibitions are now a real, provable gate instead of a permanent, unsatisfiable `gaps_found`** — the deferred ENFORCEMENT half of ADR-550 Decision 5d (the "heavy half" that #644 / PR #1149 deferred) has landed. A new deterministic `check prohibition-enforcement` sub-command (authored as `src/prohibition-enforcement.cts`, compiled by `build:lib` to the gitignored `gsd-core/bin/lib/prohibition-enforcement.cjs`) is the missing PRODUCER: it locates the wired mechanical check, confirms it is fail-first (`regression-must-fail-first`), runs it, builds `enforcementEvidence`, and emits the `dispositionForProhibition()` verdict. The previously-unreachable green branch in `dispositionForProhibition()` is now reachable from the live pipeline — a test-tier prohibition with a PASSING wired check disposes `green` and can reach `passed`, while a missing, failing, or non-fail-first check hard-gates (flagged, never green → `gaps_found`) in BOTH interactive and autonomous modes (ADR-550 D4 / D3). `verify-phase.md` wires the consumer; the green/fail-closed policy in `src/probe-core.cts` is untouched. Both wired-check kinds are accepted (ADR-550 D2): a `node --test` negative test AND a lint/AST rule, anchored on the in-tree `no-source-grep` rule (dogfooding, ADR-550 D4). This enforcement seam is the concrete instance of ADR-857 open-question §147 and lands on the core verify rail, never in `capabilities/` (D6). (#1259)
+**Test-tier prohibitions are now a real, provable gate instead of a permanent, unsatisfiable `gaps_found`** — the deferred ENFORCEMENT half of ADR-550 Decision 5d (the "heavy half" that #644 / PR #1149 deferred) has landed. A new deterministic `check prohibition-enforcement` sub-command (authored as `src/prohibition-enforcement.cts`, compiled by `build:lib` to the gitignored `gsd-core/bin/lib/prohibition-enforcement.cjs`) is the missing PRODUCER: it locates the wired mechanical check, runs it for a genuine **non-vacuous** pass, builds `enforcementEvidence`, and emits the `dispositionForProhibition()` verdict. The previously-unreachable green branch in `dispositionForProhibition()` is now reachable from the live pipeline — a test-tier prohibition with a genuinely-passing wired check disposes `green` and can reach `passed`, while a missing, non-attested, or non-passing check hard-gates (flagged, never green → `gaps_found`) in BOTH interactive and autonomous modes (ADR-550 D4 / D3). `verify-phase.md` wires the consumer; the green/fail-closed policy in `src/probe-core.cts` is untouched. Both wired-check kinds are accepted (ADR-550 D2): a `node --test` negative test (requiring a real reported test — an empty file, which `node --test` counts as one passing "test", does NOT green) AND a lint/AST rule run as `eslint --format json` filtered by `ruleId` (so plugin rules like `local/*` load — bare `--rule` cannot), anchored on the in-tree `local/no-source-grep` rule (dogfooding, ADR-550 D4). This enforcement seam is the concrete instance of ADR-857 open-question §147 and lands on the core verify rail, never in `capabilities/` (D6). (#1259)
 
-**Correction to the issue body (#1259):** the issue's "96 invalid/error negative-proof cases" figure is wrong. The definitive count is **26 invalid cases / 23 error-expectation objects** across all rule-test files; the `no-source-grep` anchor itself has exactly **2 invalid cases** (`tests/eslint-rules.test.cjs`, the `.includes()` and `.match()` invalid blocks). Those 2 cases ARE genuine `regression-must-fail-first` proofs, so the anchor argument is unaffected — but the count is "the 2 `no-source-grep` invalid cases," not 96.
+**Honest scope — `failFirst` is caller-attested, not yet machine-proven.** This lands the *execution + non-vacuous-pass* half: the producer requires the caller to attest `failFirst: true` and the check to genuinely run and pass. It does NOT yet independently prove the check *fails-on-violation* (the literal `regression-must-fail-first` property) — cheap proof of that at verify time needs running the check against a known violation fixture, which is a **tracked follow-up**. The red-first property currently rests on caller attestation, surfaced transparently in the evidence record.
+
+**Correction to the issue body (#1259):** the issue's "96 invalid/error negative-proof cases" figure is wrong. For the `no-source-grep` anchor specifically, the genuine `regression-must-fail-first` proofs are its **two `invalid` cases** (the `.includes()` and `.match()` blocks) in `tests/eslint-rules.test.cjs` — not 96. The anchor argument is unaffected (those two cases ARE real fail-first proofs); only the count was off.