feat: Add swarm-coordination plugin for multi-agent conflict prevention

Implements three complementary patterns for coordinating multi-agent swarms:

1. Status Polling (Fix 1): Orchestrator periodically spawns status-checker
   agents to monitor swarm health, detect stuck agents, and identify
   conflicts early.

2. File Claiming (Fix 2): Agents claim file ownership before editing via
   a claims registry (.claude/file-claims.md). Prevents multiple agents
   from editing the same file simultaneously.

3. Checkpoint-Based Orchestration (Fix 5): Separates swarm execution into
   phases - planning (read-only), conflict detection, resolution, then
   implementation with monitoring.

Plugin contents:
- /swarm command for full orchestrated workflow
- status-checker agent (haiku, lightweight polling)
- conflict-detector agent (analyzes plans for overlaps)
- plan-reviewer agent (validates individual plans)
- swarm-patterns skill with comprehensive documentation

plugins/swarm-coordination/skills/swarm-patterns/examples/simple-swarm.md

@@ -0,0 +1,260 @@
+# Simple Swarm Example
+
+A two-agent swarm implementing a feature with coordinated file claiming.
+
+## Scenario
+
+Task: Add user authentication to an Express API
+
+## Initial Setup
+
+### Swarm Status File
+`.claude/swarm-status.json`:
+```json
+{
+  "swarm_id": "auth-feature-001",
+  "task": "Add user authentication",
+  "started": "2025-01-15T10:00:00Z",
+  "phase": "initialized",
+  "agents": {}
+}
+```
+
+### File Claims Registry
+`.claude/file-claims.md`:
+```markdown
+# File Claims Registry
+
+Last updated: 2025-01-15T10:00:00Z
+Swarm ID: auth-feature-001
+
+| Agent ID | File Path | Claimed At | Status |
+|----------|-----------|------------|--------|
+```
+
+## Phase 1: Planning
+
+Launch two planning agents:
+
+**Agent 1 Prompt**:
+```
+Analyze the codebase and create an implementation plan for:
+Adding JWT token validation middleware
+
+You are in PLANNING MODE - DO NOT modify any files.
+Output a structured plan with all files you need to modify.
+```
+
+**Agent 2 Prompt**:
+```
+Analyze the codebase and create an implementation plan for:
+Adding user login/logout API endpoints
+
+You are in PLANNING MODE - DO NOT modify any files.
+Output a structured plan with all files you need to modify.
+```
+
+### Agent 1 Plan Output
+`.claude/swarm-plans/jwt-middleware.md`:
+```markdown
+## Agent Plan: jwt-middleware
+
+### Task Summary
+Implement JWT token validation middleware for protected routes.
+
+### Files to Modify
+- `src/middleware/index.ts`: Export new auth middleware
+
+### Files to Create
+- `src/middleware/auth.ts`: JWT validation middleware
+- `src/types/auth.ts`: Token payload types
+
+### Dependencies
+- Requires: None
+- Blocks: Protected routes need this middleware
+
+### Implementation Steps
+1. Create auth types
+2. Implement JWT validation middleware
+3. Export from middleware index
+```
+
+### Agent 2 Plan Output
+`.claude/swarm-plans/auth-endpoints.md`:
+```markdown
+## Agent Plan: auth-endpoints
+
+### Task Summary
+Implement login and logout API endpoints.
+
+### Files to Modify
+- `src/routes/index.ts`: Add auth routes
+- `src/middleware/index.ts`: Import auth utilities
+
+### Files to Create
+- `src/routes/auth.ts`: Login/logout endpoints
+- `src/services/auth.ts`: Authentication service
+
+### Dependencies
+- Requires: JWT middleware for logout validation
+- Blocks: None
+
+### Implementation Steps
+1. Create auth service
+2. Implement auth routes
+3. Update routes index
+4. Update middleware index
+```
+
+## Phase 2: Conflict Detection
+
+Analyzing plans:
+
+```
+File: src/middleware/index.ts
+  - jwt-middleware: modify (export new middleware)
+  - auth-endpoints: modify (import auth utilities)
+  → CONFLICT DETECTED
+```
+
+### Conflict Report
+```markdown
+## Conflict Analysis
+
+### Conflicts Found: 1
+
+#### Conflict 1: src/middleware/index.ts
+Agents: jwt-middleware, auth-endpoints
+Nature: Both agents plan to modify this file
+- jwt-middleware: Add export for auth middleware
+- auth-endpoints: Import auth utilities
+
+**Resolution Options**:
+1. Sequential: jwt-middleware first, then auth-endpoints
+2. Merge: Have jwt-middleware handle all middleware/index.ts changes
+```
+
+## Phase 3: Resolution
+
+**Chosen Resolution**: Option 1 - Sequential execution
+
+Updated execution plan:
+- Batch 1: jwt-middleware (no dependencies)
+- Batch 2: auth-endpoints (after jwt-middleware completes)
+
+## Phase 4: File Claiming
+
+Updated `.claude/file-claims.md`:
+```markdown
+# File Claims Registry
+
+Last updated: 2025-01-15T10:05:00Z
+Swarm ID: auth-feature-001
+
+| Agent ID | File Path | Claimed At | Status |
+|----------|-----------|------------|--------|
+| jwt-middleware | src/middleware/auth.ts | 2025-01-15T10:05:00Z | claimed |
+| jwt-middleware | src/middleware/index.ts | 2025-01-15T10:05:00Z | claimed |
+| jwt-middleware | src/types/auth.ts | 2025-01-15T10:05:00Z | claimed |
+| auth-endpoints | src/routes/auth.ts | 2025-01-15T10:05:00Z | pending |
+| auth-endpoints | src/routes/index.ts | 2025-01-15T10:05:00Z | pending |
+| auth-endpoints | src/services/auth.ts | 2025-01-15T10:05:00Z | pending |
+```
+
+Note: auth-endpoints claims are "pending" until jwt-middleware completes.
+
+## Phase 5: Implementation
+
+### Batch 1: jwt-middleware
+
+Launch jwt-middleware agent with implementation instructions:
+```
+Execute your approved plan from .claude/swarm-plans/jwt-middleware.md
+Only modify files claimed by jwt-middleware in .claude/file-claims.md
+```
+
+**Status after 45 seconds** (from status-checker):
+```json
+{
+  "overall_health": "healthy",
+  "agents": {
+    "jwt-middleware": {"status": "working", "progress": "Creating middleware"}
+  }
+}
+```
+
+**Status after 2 minutes**:
+```json
+{
+  "overall_health": "healthy",
+  "agents": {
+    "jwt-middleware": {"status": "completed"}
+  }
+}
+```
+
+### Release Claims & Activate Batch 2
+
+Updated `.claude/file-claims.md`:
+```markdown
+| jwt-middleware | src/middleware/auth.ts | 2025-01-15T10:05:00Z | released |
+| jwt-middleware | src/middleware/index.ts | 2025-01-15T10:05:00Z | released |
+| jwt-middleware | src/types/auth.ts | 2025-01-15T10:05:00Z | released |
+| auth-endpoints | src/routes/auth.ts | 2025-01-15T10:07:00Z | claimed |
+| auth-endpoints | src/routes/index.ts | 2025-01-15T10:07:00Z | claimed |
+| auth-endpoints | src/services/auth.ts | 2025-01-15T10:07:00Z | claimed |
+| auth-endpoints | src/middleware/index.ts | 2025-01-15T10:07:00Z | claimed |
+```
+
+Note: auth-endpoints now also claims middleware/index.ts after jwt-middleware released it.
+
+### Batch 2: auth-endpoints
+
+Launch auth-endpoints agent with implementation instructions.
+
+**Status after 3 minutes**:
+```json
+{
+  "overall_health": "healthy",
+  "agents": {
+    "jwt-middleware": {"status": "completed"},
+    "auth-endpoints": {"status": "completed"}
+  },
+  "completion_percentage": 100
+}
+```
+
+## Phase 6: Verification
+
+Checks:
+- [x] jwt-middleware completed
+- [x] auth-endpoints completed
+- [x] All files modified as planned
+- [x] No orphaned claims
+- [x] Build succeeds
+- [x] Tests pass
+
+## Phase 7: Summary
+
+```markdown
+## Swarm Completion Report
+
+### Task: Add user authentication
+### Duration: 8 minutes
+### Agents: 2
+
+### Files Created
+- src/middleware/auth.ts
+- src/types/auth.ts
+- src/routes/auth.ts
+- src/services/auth.ts
+
+### Files Modified
+- src/middleware/index.ts
+- src/routes/index.ts
+
+### Conflicts Resolved
+- 1 conflict on src/middleware/index.ts (sequential resolution)
+
+### Status: SUCCESS
+```