feat(mvp): working secrets-engine CLI for the whynot-design npm publish lane

Implements SECRETS-WP-0002 end to end as a uv-managed Python package:

- catalog: non-secret lane registry + strict validator (build/test/prod)
- stage roles + OpenBao ACL policies; guards refuse wildcards, sys/, identity/,
  admin names, and cross-stage paths before any backend call
- plan/apply: dry-run-first, idempotent policy + approle apply, decision-gated
- decisions: State Hub lookup with local-fixture fallback; non-secret evidence
  to JSONL + hub progress, scrubbed of any value
- provision/verify: mode-0600 file import + generated test values; positive/
  negative checks that never print the value
- exec delivery: `exec --catalog ... -- npm publish` injects the token via a
  temp .npmrc for the child only, cleaned up on exit/failure/interrupt
- ops-warden routing contract + hardening backlog docs
- 34 tests incl. live OpenBao integration; scripts/demo-e2e.sh runs the full
  chain against a throwaway bao dev server

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

src/secrets_engine/__init__.py

@@ -0,0 +1,12 @@
+"""secrets-engine: decision-aware workflow layer over OpenBao.
+
+OpenBao enforces custody, policy, lease, and audit. This package owns the
+operator/agent interaction model: catalog, decision checks, plan/apply, safe
+provisioning, verification, exec-time delivery, and non-secret evidence.
+
+Hard rule enforced throughout the code: raw secret *values* never enter logs,
+evidence, State Hub payloads, return values, or stdout. Values live only in
+OpenBao, transient process memory, and short-lived mode-0600 files.
+"""
+
+__version__ = "0.1.0"