Implemented multi-user connection handling with user identity tracking
(TeamMember with owner/admin/member/viewer roles), role-based access
control (TeamPermission with read/write/admin/manage_members), concurrent
session support (SessionRegistry with thread-safe locking and per-user/
per-project queries), and optimistic-locking conflict resolution
(VersionStamp with last-writer-wins, reject, and merge strategies).
Added TeamCollaborationService as the central orchestrator for all
collaboration operations: team membership management, permission
enforcement, session lifecycle, and version-stamp conflict detection/
resolution. The service cleans up user sessions when members are removed.
Domain models follow existing patterns: Pydantic BaseModel with
ConfigDict, StrEnum enums, ULID identifiers, and an error hierarchy
rooted in TeamCollaborationError.
Includes 48 Behave BDD scenarios (178 steps) covering all models,
service operations, and edge cases, plus 15 Robot Framework integration
tests for end-to-end workflow validation.
ISSUES CLOSED: #863
