Bootstrap hotpath from engineering spec v0.1

Commit the spec and scaffold the system it describes:

- SPEC.md: the full v0.1 engineering spec
- crates/: trust-layer Rust workspace, unit-tested
  - bench-runner: interleaved ABAB scheduling with discarded warm-ups,
    deterministic bootstrap CIs over the ratio of medians,
    CI-lower-bound accept rule, env fingerprinting, and a CLI with
    compare + A/A self-test modes (A/A verified passing end-to-end)
  - diff-test: gate outcome model, sha256 corpus pin verifier that
    refuses on mismatch, per-target equivalence policy parser
    (byte-identical default, explicit fp-tolerance opt-in)
  - ledger: append-only SQLite attempt schema with UPDATE/DELETE
    refused by triggers, anti-double-attempt query
  - report: cores-saved and dollars/yr ROI math over speedup CIs,
    pricing.toml inputs
- playbook/: classes 1-7 with preconditions, procedure, verification
  notes, and known failure modes per class
- agent/: Python package skeleton — six-tool contract and prompting
  spine, harness IPC deferred to Phase 1
- config/: accept.toml (2% threshold, 30 runs/side), pricing.toml
- targets/, corpora/, results/calibration/: layout and policy docs

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

config/accept.toml

@@ -0,0 +1,20 @@
+# Accept thresholds for bench-runner (SPEC §3.1).
+# This file is trust-layer: read-only to the agent (SPEC §10).
+
+# CI lower bound of the speedup ratio must clear 1 + threshold.
+threshold = 0.02
+
+# Measured runs per side (SPEC minimum: 30). Interleaved ABAB.
+runs_per_side = 30
+
+# Warm-up runs per side, discarded.
+warmup_runs = 3
+
+# Bootstrap resamples for the ratio CI.
+bootstrap_iters = 10000
+
+# Confidence level for the ratio CI.
+confidence = 0.95
+
+# Fixed PRNG seed so calibration runs are reproducible.
+bootstrap_seed = 1887343589