gates: verdict pipeline — gates + bench + ledger row, pristine-rebuilt baselines

Adds crates/verdict ('just verdict'): runs the core gates on the
candidate binary, then an interleaved A/B bench vs the baseline with
the CI-lower-bound rule, and writes the append-only ledger row with
per-side median CIs, workload statement, and env fingerprint. Gate
failure short-circuits to rejected-gate; --needs-human-review caps an
accepted verdict (never upgrades). CPU pinning moves into accept.toml
(pin_prefix, machine-specific, applied to both sides identically).

The smoke test caught a real trust gap: pointing --baseline-bin at the
workspace build (phase1-verdict-smoke-001) measured patched-vs-patched
and returned null, because gate runs rebuild the workspace binary from
the patched tree. Fix: --rebuild-baseline stashes the patch, builds
the baseline into isolated targets/<name>/baseline/, and restores the
patch — SPEC 3.1's pristine-checkout rule, now enforced by the
harness. Re-run (phase1-verdict-smoke-002) reproduces the Phase 0
result mechanically: +10.4% median, 95% CI [1.0932, 1.1137], accepted.
Both smoke rows are in the ledger, including the null one.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EcKPWQ3MQD4NdEHwar96u2

justfile

@@ -38,3 +38,12 @@ calibrate cmd out sessions="20":
 # upstream tests -> golden replay. Fuzz/sanitizers stay per-attempt.
 gates target:
     cargo run -p diff-test -- {{target}}
+
+# One-shot attempt verdict: gates on candidate -> interleaved A/B vs a
+# pristine-rebuilt baseline -> ledger row. Extra flags pass through
+# (--patch-file, --needs-human-review, --baseline-bin).
+verdict target candidate run_id class hypothesis hotspot *flags:
+    cargo run -p verdict -- {{target}} --rebuild-baseline \
+        --candidate-bin "{{candidate}}" --run-id "{{run_id}}" \
+        --playbook-class {{class}} --hypothesis "{{hypothesis}}" \
+        --hotspot "{{hotspot}}" {{flags}}