feat: Add Claude Code plugin for beads [addresses #28]

Adds a Claude Code plugin for one-command installation of beads via
/plugin command. The plugin bundles the MCP server, slash commands,
and an autonomous task agent.

Components:
- Plugin metadata with MCP server configuration
- 8 slash commands for core workflow (/bd-ready, /bd-create, etc.)
- Task agent for autonomous execution (@task-agent)
- Comprehensive plugin documentation (PLUGIN.md)

The plugin provides a lower-friction installation path for Claude Code
users who want integrated slash commands rather than direct MCP tools.

Related: https://github.com/steveyegge/beads/issues/28

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

.claude-plugin/commands/bd-workflow.md

@@ -0,0 +1,59 @@
+---
+description: Show the AI-supervised issue workflow guide
+---
+
+Display the beads workflow for AI agents and developers.
+
+# Beads Workflow
+
+Beads is an issue tracker designed for AI-supervised coding workflows. Here's how to use it effectively:
+
+## 1. Find Ready Work
+Use `/bd-ready` or the `ready` MCP tool to see tasks with no blockers.
+
+## 2. Claim Your Task
+Update the issue status to `in_progress`:
+- Via command: `/bd-update <id> in_progress`
+- Via MCP tool: `update` with `status: "in_progress"`
+
+## 3. Work on It
+Implement, test, and document the feature or fix.
+
+## 4. Discover New Work
+As you work, you'll often find bugs, TODOs, or related work:
+- Create issues: `/bd-create` or `create` MCP tool
+- Link them: Use `dep` MCP tool with `type: "discovered-from"`
+- This maintains context and work history
+
+## 5. Complete the Task
+Close the issue when done:
+- Via command: `/bd-close <id> "Completed: <summary>"`
+- Via MCP tool: `close` with reason
+
+## 6. Check What's Unblocked
+After closing, check if other work became ready:
+- Use `/bd-ready` to see newly unblocked tasks
+- Start the cycle again
+
+## Tips
+- **Priority levels**: 0=critical, 1=high, 2=medium, 3=low, 4=backlog
+- **Issue types**: bug, feature, task, epic, chore
+- **Dependencies**: Use `blocks` for hard dependencies, `related` for soft links
+- **Auto-sync**: Changes automatically export to `.beads/issues.jsonl` (5-second debounce)
+- **Git workflow**: After `git pull`, JSONL auto-imports if newer than DB
+
+## Available Commands
+- `/bd-ready` - Find unblocked work
+- `/bd-create` - Create new issue
+- `/bd-show` - Show issue details
+- `/bd-update` - Update issue
+- `/bd-close` - Close issue
+- `/bd-workflow` - Show this guide (you are here!)
+
+## MCP Tools Available
+Use these via the beads MCP server:
+- `ready`, `list`, `show`, `create`, `update`, `close`
+- `dep` (manage dependencies), `blocked`, `stats`
+- `init` (initialize bd in a project)
+
+For more details, see the beads README at: https://github.com/steveyegge/beads