feat(mcp): migrate to mcp 2.x (MCPServer) (#23)

Co-authored-by: claude <[email protected]>

CLAUDE.md

@@ -161,7 +161,7 @@ template's PLAN.md.
 │       ├── becks_pfr.py
 │       └── becks_products.py
 ├── rag/                          # chunk + embed + Chroma + BM25
-├── docs_mcp/                     # FastMCP server + lessons.md
+├── docs_mcp/                     # MCPServer (mcp 2.x) + lessons.md
 ├── eval/                         # Golden-query harness
 └── scripts/                      # registry_gc.py, usage_report.py
 ```
@@ -189,7 +189,8 @@ template's PLAN.md.
 - **Lexical store**: SQLite FTS5
 - **Fusion**: RRF k=60
 - **Transport**: streamable-HTTP in prod, stdio for local dev
-- **MCP framework**: FastMCP with `stateless_http=True`
+- **MCP framework**: `mcp` 2.x `MCPServer` (the 1.x `FastMCP`), with
+  `stateless_http=True` passed to `run()`
 
 ### Image name and package linking are repo-name-derived
 
@@ -230,7 +231,9 @@ python -m eval.run_eval --queries eval/queries.jsonl --output eval/results/basel
 - **Reranker per-pair token limit**: jina-reranker GGUF rejects the
   ENTIRE batch if any doc exceeds `n_ctx_train=1024`. Truncate
   reranked docs to ~2000 chars.
-- **FastMCP `stateless_http=True`**: critical for prod.
+- **`stateless_http=True`**: critical for prod. Under mcp 2.x it is a
+  `run()` kwarg, NOT a constructor arg — every transport option moved off
+  the constructor. `mcp.settings` no longer exists.
 - **Runner shell is `/bin/sh` (dash)** in CI — no `${VAR::N}`.
 - **Cloudflare 100 MB body cap**: push via LAN endpoint
   `192.168.0.2:1234`, pull via `git.jpaul.io`.