Phase 5 P2-3: Team dashboard + agent status API + sub-agent tree

[krusty-agent]

Summary

• add Phase 5 team dashboard page (/team) with agent cards and sub-agent tree
• add Convex agentTeam module with:
  • upsertAgentStatus (idle/working/error + current task)
  • listTeamAgents, getTeamTree, getTeamSummary
  • initial auto-archive behavior for sub-agents when idle + no current task
• extend agent HTTP API with:
  • GET /api/agent/team
  • POST /api/agent/team/status
• wire routes into existing Convex HTTP router
• add Home quick action entry to Team dashboard

Validation

• ✅ npm run mission-control:validate-observability
• ⚠️ npm run build currently fails on pre-existing repo issues unrelated to this PR:
  • missing generated API type members for didLogs / didResources
  • existing CalendarView/ListView prop mismatch (userDid)

Backlog mapping

• ✅ Team dashboard
• ✅ Agent status API (idle/working/error + current task)
• ✅ Initial sub-agent tree model + auto-archive behavior