[codex] Cascade service deletion state

[pq198363-ops]

Closes #88.

Summary

• cascade service deletion by clearing the service metadata and disabled-state stores
• emit a service.deleted audit event when a registered service is deleted
• document that outstanding usage accumulators are retained for historical metering until settlement or reset

Verification

• RED: npm run build; $env:NODE_ENV='test'; node --test dist/services-delete.test.js failed before implementation because metadata/disabled state remained and no service.deleted event was emitted
• GREEN focused: npm run build; $env:NODE_ENV='test'; node --test dist/services-delete.test.js passed 4 tests
• Full: npx prettier --check README.md src/routes/services.ts src/services-delete.test.ts
• Full: npm run lint
• Full: clean dist/, npm run build, then $env:NODE_ENV='test'; node --test dist/*.test.js dist/**/*.test.js passed 93 tests across 11 suites
• Full: git diff --check