v0.13.0

feat(v0.13.0): distributed workers — mailbox + shared task list (#1+2)

Workers (and the orchestrator) can now coordinate peer-to-peer through
six new MCP tools instead of every information path going through the
orchestrator.

New file: server/agent-mcp.mjs — stdio MCP server exposing:
  - send_message(from, to, content): peer-to-peer DM, lands in target's inbox
  - read_inbox(from): drain your own incoming messages
  - create_task(from, title, description?, assignee?): add to shared task board
  - list_tasks(from, status?): see pending / in_progress / completed across team
  - claim_task(from, id): self-assign a pending task
  - complete_task(from, id, summary?): mark done with outcome

Every call carries 'from' = the caller's worker key, since all subagents
spawned from one claude session share the same MCP server instance and
env vars can't differentiate per-worker. The orchestrator's
buildAgentsFlag now prepends a worker-key + coord-tool instruction to
each worker's role prompt so they know their key and how to use the
tools.

Server (server.mjs):
  - inboxes: Map<sessionId, Map<workerKey, Message[]>>
  - taskLists: Map<sessionId, Task[]>
  - HTTP endpoints under /agent/* that agent-mcp.mjs proxies to
  - emitAgentEvent broadcasts coordination activity (✉ A→B, ＋ task, ▸ claim,
    ✓ complete) as system chat messages so the user sees the workflow
  - MCP config in claude spawn now includes BOTH permission + agent servers
  - Orchestrator system prompt teaches when to use the task board vs the
    Agent tool, and tells workers to call read_inbox at the start of work

Build:
  - copy + asarUnpack agent-mcp.mjs alongside permission-mcp.mjs

UI work intentionally minimal for MVP — coordination activity surfaces in
the chat log via system messages. Dedicated task / inbox panels can come
in a follow-up.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>