Define Backend POC room lifecycle and errors

[VoldemLive]

Type of Changes

	Type
	🐛 Bug fix
	✨ New feature
	🔨 Refactoring
	💯 Add tests
	🔗 Update dependencies
✓	📜 Docs

Description

The Backend POC documentation defined event payloads but did not fully specify lifecycle transitions, error precedence, or event-specific error conditions. This change makes room behavior deterministic for implementation and integration tests, synchronizes the related plans, and removes the obsolete credentialType field from the documented IceServer shape.

Related Issue

Closes #2

Updates

Before

• UI: Not applicable — documentation-only change.
• Leave, disconnect, replacement-peer, and empty-room transitions were not fully defined.
• Stable error codes did not have deterministic precedence or complete triggering conditions.
• The documented IceServer included obsolete OAuth-related fields.

After

• UI: Not applicable — documentation-only change.
• The POC lifecycle now covers create, join, either-peer leave/disconnect, replacement join, and empty-room cleanup.
• Error precedence, event-specific conditions, atomicity, and requester-only delivery are documented.
• Deferred production TTL, rate limits, maximum room counts, and authorization are clearly separated from POC behavior.
• Protocol, POC plan, and testing strategy are synchronized.
• IceServer now matches the current browser contract used by the project.

Acceptance Criteria

• The POC room lifecycle documents create, join, either-peer leave, either-peer disconnect, and empty-room cleanup behavior.
• Stable POC error codes and their triggering conditions are documented.
• Room capacity is documented as two equal peers; creator/joiner identities define negotiation duties only.
• Deferred TTL, rate-limit, and production authorization behavior is explicitly excluded.
• Relevant protocol and testing documentation is updated.

Testing Steps / QA Criteria

• git diff --check main...HEAD — passed.
• node --check server/src/index.js — passed.
• Custom Node documentation validation for balanced code fences, relative links, synchronized error codes, and stale ICE fields — passed.
• Automated project tests were not run because this is a documentation-only change and the project does not define test scripts yet.