## Summary
- add the provider boundary catalog, boundary support types, and guardrails for platform-core versus provider-owned seams
- harden provider gateway, identity resolution, operation registry, and start-gate behavior to require explicit provider bindings
- add unit and feature coverage for boundary classification, runtime preservation, unsupported paths, and platform-core leakage guards
- add the full Spec Kit artifact set for spec 237 and update roadmap/spec-candidate tracking
## Validation
- `cd apps/platform && ./vendor/bin/sail artisan test --compact tests/Unit/Providers/ProviderBoundaryClassificationTest.php tests/Unit/Providers/ProviderBoundaryGuardrailTest.php tests/Feature/Providers/ProviderBoundaryHardeningTest.php tests/Feature/Providers/UnsupportedProviderBoundaryPathTest.php tests/Feature/Guards/ProviderBoundaryPlatformCoreGuardTest.php`
- `cd apps/platform && ./vendor/bin/sail artisan test --compact tests/Unit/Providers/ProviderGatewayTest.php tests/Unit/Providers/ProviderIdentityResolverTest.php tests/Unit/Providers/ProviderOperationStartGateTest.php`
- `cd apps/platform && ./vendor/bin/sail bin pint --dirty --format agent`
- browser smoke: `http://localhost/admin/provider-connections?tenant_id=18000000-0000-4000-8000-000000000180` loaded with the local smoke user, the empty-state CTA reached the canonical create route, and cancel returned to the scoped list
Co-authored-by: Ahmed Darrazi <ahmed.darrazi@live.de>
Reviewed-on: #273
