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>

docs/src/isolation.md

@@ -34,6 +34,35 @@ The SDK's tool allow/deny list is defense-in-depth, not the boundary —
   path into the repo is the harnessd Unix socket; the trust layer is owned
   by another uid. This is the production shape (`docs/infra.md`).
 
+## Network isolation on the verdict path
+
+Target code should not be able to phone home during a measurement. What
+is actually enforced, stated honestly:
+
+- **The agent path is wrapped.** When `harnessd` launches the verdict
+  pipeline, it execs through `scripts/no-net.sh`, which runs it inside an
+  unprivileged **network namespace** (`unshare --net --map-current-user`).
+  `HOTPATH_VERDICT_WRAPPER` overrides the wrapper.
+- **It fails closed.** Where namespaces are unavailable the wrapper **exits
+  97 without running the pipeline** — it does not degrade silently. The one
+  bypass, `HOTPATH_ALLOW_UNISOLATED=1`, runs the pipeline **with full
+  network access**; it warns loudly on stderr *and* the resulting ledger row
+  records the isolation note `no-net.sh (HOTPATH_ALLOW_UNISOLATED=1 —
+  network NOT isolated)`. A run cannot claim an isolation it did not have.
+- **In CI**, the bench workload runs under `docker run --network=none`.
+
+Two limits, stated plainly rather than buried:
+
+- **Only the harnessd (agent) path is wrapped.** A human who invokes
+  `just verdict` directly runs it **unwrapped on the host**; those rows are
+  stamped `isolation: "unwrapped-host"` in the ledger. The wrapper is a
+  property of the agent pipeline, not of the `verdict` binary.
+- **Full-container isolation is still an open gap.** The namespace isolates
+  the *network* — not the filesystem, not the syscall surface. The
+  fully containerized, seccomp-restricted bench container of SPEC §10 is
+  **not built**. The agent-side OS boundary above is a separate mechanism
+  and *is* shipped.
+
 ## The two times the pipeline was wrong
 
 Anti-reward-hacking is not "it never fails" — it is "when it fails, the