feat(policy): netkingdom maturity-gated publication-scope policy

Token scope is now bound to package maturity, gated on netkingdom's own maturity:
- maturity-build -> gitea-wide, maturity-test -> org-wide, maturity-prod -> repo-scoped
  (scope narrows as stakes rise; broad tokens only for low-stakes build artifacts)
- the graduated table is DORMANT until netkingdom reaches production grade; until
  then every lane clamps to repo-scope, injected as NPM_AUTH_TOKEN (fail-safe)
- token env-var name signals blast radius: NPM_AUTH_TOKEN (repo default),
  NPM_AUTH_COULOMB_TOKEN (org), NPM_AUTH_GITEA_TOKEN (gitea), NPM_AUTH_WHYNOT_TOKEN
  (npm scope, defined but unused), NPM_AUTH_WHYNOTDESIGN (explicit repo)

netkingdom is at maturity-build today, so whynot-design resolves to repo-scope /
NPM_AUTH_TOKEN. Flip netkingdom_maturity to maturity-prod to activate graduation.

- policies/netkingdom-publication-scope.yaml: the policy data + gate
- publication_policy.py: load + resolve (clamp/active, env naming, override)
- exec delivery injects under the resolved env-var name (was fixed SE_NPM_TOKEN)
- catalog lane carries delivery_config.npm.maturity
- new CLI: `secrets-engine policy publication <lane>`
- docs/publication-scope-policy.md; tests for clamp, graduation, naming, override

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

README.md

@@ -48,6 +48,7 @@ SECRETS_ENGINE_HUB_URL="" bash scripts/demo-e2e.sh
 ```
 
 - CLI reference: [docs/cli.md](docs/cli.md)
+- Publication-scope policy (maturity → token scope): [docs/publication-scope-policy.md](docs/publication-scope-policy.md)
 - Stage roles & bootstrap tokens: [docs/openbao-stage-roles.md](docs/openbao-stage-roles.md)
 - ops-warden routing contract: [docs/ops-warden-routing-contract.md](docs/ops-warden-routing-contract.md)
 - Hardening backlog (exit bootstrap mode): [docs/hardening-backlog.md](docs/hardening-backlog.md)