[Neup123]

Summary

• keep one backward-compatible Delete Message endpoint
• automatically select the strongest permitted scope:
  • connected account message: delete for everyone
  • another participant's group message while admin: delete for everyone
  • another participant's direct message or group message without admin permission: delete for this account
• fall back to delete for this account when a revoke cannot be confirmed
• report the applied scope and confirmation state explicitly
• expose guided Swagger form fields while retaining JSON input
• document request fields, webhook mappings, response semantics, and fallback reasons
• add focused deletion and runtime OpenAPI validation

Validation

• npm run test:delete-message
• npm run lint:check
• npm run audit:runtime-openapi
• npm run audit:chat-docs
• npx tsc --noEmit
• npm run build
• git diff --check

Refs #22
Fixes #28