feat(agent-mail): Add Python adapter library for Agent Mail integration

- Created lib/beads_mail_adapter.py with AgentMailAdapter class
- Automatic health check on initialization
- Graceful degradation when server unavailable
- Methods: reserve_issue(), release_issue(), notify(), check_inbox()
- Environment-based configuration (AGENT_MAIL_URL, AGENT_MAIL_TOKEN)
- Comprehensive unit tests (15 tests, 100% passing)
- Full documentation in lib/README.md

Closes bd-m9th

Amp-Thread-ID: https://ampcode.com/threads/T-caa26228-0d18-4b35-b98a-9f95f6a099fe
Co-authored-by: Amp <amp@ampcode.com>

AGENT_MAIL_INTEGRATION_STATUS.md

@@ -1,25 +1,44 @@
 # MCP Agent Mail Integration - Current Status
 
-## Completed
-- ✅ **bd-muls**: MCP Agent Mail server installed and tested locally
-  - Server running successfully on port 8765
-  - Web UI accessible at http://127.0.0.1:8765/mail
-  - Installation location: `mcp_agent_mail/`
+## Proof of Concept ✅ COMPLETE
 
-## Known Issues
-- ⚠️ MCP API tool execution errors when calling `ensure_project`
-  - Core HTTP infrastructure works
-  - Web UI functional  
-  - Needs debugging of tool wrapper layer
+**Epic:** bd-spmx (Investigation & Proof of Concept) - CLOSED
 
-## Next Ready Work
-- **bd-6hji** (P0): Test exclusive file reservations with two agents
-  - Requires working MCP API (fix tool execution first)
+### Completed Validation
+- ✅ **bd-muls**: Server installed and tested (~/src/mcp_agent_mail)
+- ✅ **bd-27xm**: MCP API tool execution issues resolved
+- ✅ **bd-6hji**: File reservation collision prevention validated
+  - Two agents (BrownBear, ChartreuseHill) tested
+  - First agent gets reservation, second gets conflict
+  - Collision prevention works as expected
+- ✅ **bd-htfk**: Latency benchmarking completed
+  - Agent Mail: <100ms (HTTP API round-trip)
+  - Git sync: 2000-5000ms (full cycle)
+  - **20-50x latency reduction confirmed**
+- ✅ **bd-pmuu**: Architecture Decision Record created
+  - File: [docs/adr/002-agent-mail-integration.md](docs/adr/002-agent-mail-integration.md)
+  - Documents integration approach, alternatives, tradeoffs
+
+### Validated Benefits
+1. **Collision Prevention**: Exclusive file reservations prevent duplicate work
+2. **Low Latency**: <100ms vs 2000-5000ms (20-50x improvement)
+3. **Lightweight**: <50MB memory, simple HTTP API
+4. **Optional**: Git-only mode remains fully supported
+
+## Next Phase: Integration (bd-wfmw)
+
+Ready to proceed with integration layer implementation:
+- HTTP client wrapper for Agent Mail API
+- Reservation checks in bd update/ready
+- Graceful fallback when server unavailable
+- Environment-based configuration
 
 ## Quick Start Commands
 ```bash
-# Start server
-cd mcp_agent_mail && source .venv/bin/activate && uv run python -m mcp_agent_mail.cli serve-http
+# Start Agent Mail server (optional)
+cd ~/src/mcp_agent_mail
+source .venv/bin/activate
+uv run python -m mcp_agent_mail.cli serve-http
 
 # Access web UI
 open http://127.0.0.1:8765/mail
@@ -27,3 +46,8 @@ open http://127.0.0.1:8765/mail
 # Stop server
 pkill -f "mcp_agent_mail.cli"
 ```
+
+## Resources
+- [Latency Benchmark Results](latency_results.md)
+- [ADR 002: Agent Mail Integration](docs/adr/002-agent-mail-integration.md)
+- [Agent Mail Repository](https://github.com/Dicklesworthstone/mcp_agent_mail)