feat: add cross-team communication orchestrator
Autonomous message routing between Agent Teams via MCP with cascade
protection. Inbox-first canonical delivery with cross-process file
lock (O_CREAT|O_EXCL) and best-effort relay for online teams.
- CascadeGuard: rate limit (10/min), chain depth (max 5), pair cooldown (3s)
- FileLock: cross-process safe via kernel-level atomic lock files
- CrossTeamService: validate → cascade → file-lock → inbox write → relay → outbox
- Unified lead resolver with members.meta.json normalization (trim+dedup)
- 3 MCP tools: cross_team_send, cross_team_list_targets, cross_team_get_outbox
- Controller module with sync file lock, same protocol as main
- IPC adapter with 3 Electron handlers
- 64 new tests across 8 test files
c3eea4d6eb