Spec 435: Exchange structured output readiness (#502)
## Summary
- Add Spec 435 backend-only Exchange structured output envelope and target normalizer readiness helpers for transportRule, remoteDomain, and inboundConnector.
- Add deterministic hash input/readiness handling and no-promotion guard coverage.
- Add Spec 435 spec, plan, tasks, checklist, and implementation report artifacts.
## Validation
- git diff --cached --check
- cd apps/platform && php artisan test --filter=Spec435 --compact
## Product Surface / Deployment
- Livewire v4 compliance unchanged.
- Filament provider registration unchanged under apps/platform/bootstrap/providers.php.
- Global search unchanged; no resources added or modified.
- Destructive/high-impact actions: none.
- Asset strategy: none; no filament:assets requirement for this slice.
- Browser proof: N/A - no rendered UI surface changed.
- Deployment impact: no env vars, migrations, queues, scheduler, storage, assets, or Dokploy runtime behavior changes.
Co-authored-by: Ahmed Darrazi <ahmed.darrazi@live.de>
Reviewed-on: #502
ahmido
a09cc6ca8d