Claude host PR 4: Squad as a Claude Code plugin (#2438 Phase 5) #2443

Part of #2438 (PR 4 of the epic's PR plan, Wave 4). Starts after PR 3 merges (including Phase 3 if it was split out).

Goal

Distribute Squad as a Claude Code plugin, alongside squad init --client claude, not instead of it. Both paths keep working.

Verify first (a measurement, not code)

Someone has to run Claude Code for this. Record the result in the host matrix, not as an assumption.

• Do plugin-provided MCP servers remove the project .mcp.json approval step and the --mcp-config requirement?
  • interactive claude
  • headless claude -p

Today users run claude --agent squad --mcp-config .mcp.json, and headless runs without the flag halt on the state-backend handshake.

Scope

• Publish a Squad plugin and marketplace in github/squad, bundling:
  • the coordinator agent
  • member-agent generation (from PR 3)
  • skills (from PR 3)
  • hooks (from PR 3)
  • the squad_state MCP server
  • slash commands: /squad:ralph, /squad:cast, /squad:ceremony, /squad:status
• Moving the coordinator anchor into a plugin is a projection-version change (harness-adapters §5). Update §7 and keep squad init --client claude working for repos that don't use plugins.
• Settle open question 3 in Epic: Claude Code as a first-class Squad 2.0 host, and the non-Copilot host that promotes the v0.2 profiles #2438: does the plugin replace squad init --client claude or ship alongside it? The epic's default is alongside.

Done when

• The plugin installs and runs the coordinator, members, skills, hooks and MCP server.
• The measurement is recorded in the matrix.
• If the measurement allows it, the documented Claude quick start is one command with no --mcp-config.
• The regression guards from PR 1 stay green, and squad init --client claude still works.