Add MCP server for Claude Code memory integration

- Create stdio MCP server wrapping core memory functions (query, show, list, children, add, link)
- Add CLAUDE.md with memory-querying instructions for Claude
- Register MCP server in .mcp.json
- Document MCP setup and tools in USAGE.md

CLAUDE.md

@@ -0,0 +1,23 @@
+# Project Memory Guidelines
+
+## Before Making Changes
+- **Always query memory** before modifying code or making architectural decisions: use `memory_query` to search for relevant context.
+- Use `memory_show` to check existing context on a specific topic before acting.
+- Check for existing decisions, gotchas, and component info that may affect your changes.
+
+## After Making Changes
+- **Store new decisions** as memory nodes (kind: `decision`) when architectural choices are made.
+- **Store gotchas** as memory nodes (kind: `memory`) when you discover non-obvious behavior.
+- **Store component info** (kind: `component`) when creating or significantly modifying a module.
+- Tag nodes appropriately for future retrieval.
+
+## Memory Tools (MCP)
+- `memory_query` — search memory by text
+- `memory_show` — show a node by ID or prefix
+- `memory_list` — list nodes filtered by kind/status/tags
+- `memory_children` — list children of a node
+- `memory_add` — add a new memory node
+- `memory_link` — create a relationship between nodes
+
+## Git Preferences
+- Do not add `Co-Authored-By` lines to commits.