## 1. Engine Client

- [x] 1.1 Add `delete_document(doc_id)` method to `mcp/engine.py`

## 2. MCP Tools

- [x] 2.1 Add `kb_set_collection` tool to `mcp/server.py`
- [x] 2.2 Add `kb_delete` tool to `mcp/server.py`

## 3. Verification

- [x] 3.1 Test kb_set_collection and kb_delete against running engine