gates: close the audit findings — enforce the gates the docs claimed

An adversarial audit found the enforcement story ahead of the code: gates
that were documented as hard gates were advisory, manual, or absent, and
several human-facing claims outran the machine record. This makes the
claims true.

High findings

- Differential fuzz was documentation, not enforcement: verdict hardcoded
  fuzz_iters=0 and diff-test hardcoded the gate to Skipped, while the case
  studies claimed 10k-iteration fuzz on the same wins. Fuzz is now a real
  pipeline gate (strict FUZZ-RESULT contract, executed count recorded), and
  it is inherently baseline-vs-candidate, so it runs on the accept path and
  reports Skipped in the standalone `just gates` flow. New hard rule: a
  machine `accepted` verdict is impossible unless the fuzz gate actually
  passed — otherwise it caps at needs-human-review.
- The agent's system prompt claimed FP/concurrency/unsafe patches were
  "routed to human review automatically". No such mechanism existed. Added
  a conservative lexical risk classifier (crates/verdict/src/risk.rs) that
  forces needs-human-review on any would-be accept carrying those signals;
  fp-tolerance equivalence always signals.
- The local verdict path ran agent-influenced code unsandboxed. It now runs
  under scripts/no-net.sh (network namespace) and fails closed. Upstream
  test suites are hash-verified against corpora/<t>/TESTSUITE.sha256 when
  present (scripts/pin-testsuite.sh generates them).

Also fixed, found while fixing the above

- The pipeline script's `set -e` was inert (brace group as the left operand
  of `&&`), so a failing candidate build did not abort the run and verdict
  could bench a stale binary. Now a scoped subshell whose status is branched
  on at top level.
- A wrapper that exits before exec'ing (no-net.sh refusing, bad wrapper path)
  stranded RUNNING.lock and left read_verdict polling forever. Failure
  accounting now lives outside the wrapper.
- harnessd's patch allowlist ignored git rename/copy headers and --no-prefix
  diffs; the rename-escape case is now a committed regression test.
- The workspace did not compile on Windows (ungated Unix APIs). cfg-gated;
  71 portable tests now run on both platforms.
- pin-check regenerated the corpus manifest instead of verifying it; it is
  now verify-only, with a deliberate `just pin-corpus` to re-pin.
- Max RSS is captured per run on Unix; PMU counters are opt-in diagnostics
  (compare --perf-stat), never part of the accept decision.

Docs now match the code, including what is NOT yet enforced: no target ships
a TESTSUITE.sha256 pin, no target declares [build].tsan, and matmul is not
wired to the fp-tolerance gate — each is stated as mechanized-but-inert
rather than done. Corrected the stale "33 ledger rows" (34), the playbook's
class-3 cJSON win (rejected), adversarial-review.md's sanitizer-separation
claim (five accepted rows carry sanitizers_clean=false), the unsupported
"40,000 requests" figure, and the blanket "historical rows record
fuzz_iters=0" (8 of 10; phase0-tokei-002/-003 record 4,332).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

results/phase5/README.md

@@ -137,3 +137,31 @@ it generalize?" objection with the two hardest cases the spec named:
 
 Zero shipped false accepts, still. The product is trust, and trust
 transferred.
+
+---
+
+## Erratum (2026-07-13) — how far the kernel lane is actually wired
+
+The write-up above describes the FP-tolerance gate as though `matmul` runs
+through the standard pipeline. It does not, and the distinction matters:
+
+- **The policy is in the pipeline.** `EquivalencePolicy` is honored by
+  `diff-test`'s gate sequence (an fp-tolerance target needs a committed
+  `[corpus].golden_reference`; the gate fails closed without one), and
+  `crates/verdict` treats fp-tolerance equivalence as an automatic
+  `needs-human-review` signal. That machinery is real and unit-tested.
+- **`matmul` is not a pipeline target.** It ships `targets/matmul/kernel.c`
+  and `targets/matmul/equivalence.toml` but **no `target.toml`** — the file
+  `diff-test`/`verdict` load a target from. So the lane cannot currently be
+  run via `just gates` or `just verdict` at all.
+- **Therefore the demonstration is script-driven.**
+  `scripts/kernel-lane-demo.sh` invokes the `fp-compare` binary and
+  `bench-runner compare` directly, and the `phase5-matmul-opt` ledger row
+  was recorded **outside** the automated verdict path.
+
+Nothing in the measured result changes — the 3.23× [3.16, 3.26] speedup, the
+244,901/262,144 differing values, the rejected +0.5 perturbation, and the
+`needs-human-review` verdict all stand as printed. What was overstated is the
+*integration*: the equivalence policy is closed; wiring this target into the
+pipeline is open work. The original text stands unedited above; this note is
+the correction.