feat(agent-teams): add plugin for multi-agent team orchestration

New plugin with 7 presets (review, debug, feature, fullstack, research,
security, migration), 4 specialized agents, 7 slash commands, 6 skills
with reference docs, and Context7 MCP integration for research teams.

plugins/agent-teams/commands/team-shutdown.md

@@ -0,0 +1,50 @@
+---
+description: "Gracefully shut down an agent team, collect final results, and clean up resources"
+argument-hint: "[team-name] [--force] [--keep-tasks]"
+---
+
+# Team Shutdown
+
+Gracefully shut down an active agent team by sending shutdown requests to all teammates, collecting final results, and cleaning up team resources.
+
+## Phase 1: Pre-Shutdown
+
+1. Parse `$ARGUMENTS` for team name and flags:
+   - If no team name, check for active teams (same discovery as team-status)
+   - `--force`: skip waiting for graceful shutdown responses
+   - `--keep-tasks`: preserve task list after cleanup
+
+2. Read team config from `~/.claude/teams/{team-name}/config.json` using the Read tool
+3. Call `TaskList` to check for in-progress tasks
+
+4. If there are in-progress tasks and `--force` is not set:
+   - Display warning: "Warning: {N} tasks are still in progress"
+   - List the in-progress tasks
+   - Ask user: "Proceed with shutdown? In-progress work may be lost."
+
+## Phase 2: Graceful Shutdown
+
+For each teammate in the team:
+
+1. Use `SendMessage` with `type: "shutdown_request"` to request graceful shutdown
+   - Include content: "Team shutdown requested. Please finish current work and save state."
+2. Wait for shutdown responses
+   - If teammate approves: mark as shut down
+   - If teammate rejects: report to user with reason
+   - If `--force`: don't wait for responses
+
+## Phase 3: Cleanup
+
+1. Display shutdown summary:
+
+   ```
+   Team "{team-name}" shutdown complete.
+
+   Members shut down: {N}/{total}
+   Tasks completed: {completed}/{total}
+   Tasks remaining: {remaining}
+   ```
+
+2. Unless `--keep-tasks` is set, call `Teammate` tool with `operation: "cleanup"` to remove team and task directories
+
+3. If `--keep-tasks` is set, inform user: "Task list preserved at ~/.claude/tasks/{team-name}/"