feat(team): org-scoped coordination — teammates finally share one board

The API resolves projects against the caller's org, but this server never
sent one, so every call fell back to each user's PERSONAL org: two
teammates on the same repo silently got two disjoint boards. Coordination
'across a team' only ever worked for one account.

- project-identity: deriveOrgId (AXIS_ORG_ID env > committed
  .axis/axis.json "org" > none) carried on ProjectIdentity; the committed
  file is now the one-line way a team pins repo + org for every clone
- nerve-center: sends X-Axis-Org on every coordination call; org re-derived
  on switch_project / workspace auto-rebind; kept in sync on ContextManager
  so search/embed calls carry it too
- list_agents: merges teammates from GET /api/v1/agents (server-derived
  presence from live locks + claimed jobs) — the in-process roster only
  ever saw agents inside this one process
- cli: passes AXIS_ORG_ID through to the spawned server
- README: document the org pin; stop recommending PROJECT_NAME=default
  (it outranks repo detection and collapses every repo onto one board)
- .axis/axis.json committed for this repo; 7 new bun tests (15 pass)
- dist rebuilt, version 1.14.0 (global install already symlinks here —
  restart MCP clients to load)