Collaboration Contract v1.0 Ratification for Services, Interfaces, and RERUM

## Summary
Adopt and ratify the websocket collaboration and deferred-persistence contract for cross-repository implementation.

## Contract Source
- docs/collaboration/websocket-collaboration-contract.md

## Required Decisions
- Event envelope and versioning
- Operation schema and idempotency requirements
- Deferred flush trigger windows
- Conflict payload and reconciliation responsibilities
- Reliability guarantees and limits

## Exit Criteria
- Maintainers from TPEN-services, TPEN-interfaces, and RERUM confirm agreement
- Any deviations are tracked as follow-up issues
- Contract version marked approved for Phase 1 rollout

Start by reading docs/collaboration/websocket-collaboration-contract.md and review the listed decisions for the event envelope, operation schema, deferred flush windows, conflict handling, and reliability limits. Done means maintainers from TPEN-services, TPEN-interfaces, and RERUM agree, deviations are tracked as follow-up issues, and the contract is marked approved for Phase 1 rollout.

Written by the indexing model from the issue text.