AB#3134 Migrate to the mcp 2.0 SDK (FastMCP -> MCPServer)

[vosesoftware]

Lifts the mcp<2 cap added alongside AB#3132.

mcp 2.0 removed mcp.server.fastmcp outright and renamed the high-level server class FastMCP → MCPServer, now exported from mcp.server. That rename is essentially the whole migration: the @mcp.tool / @mcp.resource / @mcp.prompt decorators keep their signatures and still return the plain undecorated function, so the 25 tool bodies, their descriptions and their generated schemas are untouched — and the tests that call tools directly keep working.

Two real API changes

	1.x	2.0
Server class	from mcp.server.fastmcp import FastMCP	from mcp.server import MCPServer
HTTP host/port	mutate mcp.settings before run()	run(transport=..., host=..., port=...)

MCPServer also accepts version, which FastMCP had no equivalent for, so the server now reports its own version in serverInfo instead of leaving it blank. CLI flags (--transport, --host, --port) are unchanged.

Verification

pytest here runs against a fake bridge and never exercises the protocol layer, so the suite passing is necessary but nowhere near sufficient. Also checked:

• Registration compared name-for-name against the 1.x baseline, in a detached worktree at origin/main: 25 tools, 4 resources, 2 prompts — identical names, descriptions and schemas, including the AB#3123 generator output schema. (25/4/2 matches the decorator count exactly; an earlier 27/5/4 grep was counting docstring mentions.)
• Live MCP initialize handshake over stdio — the same check release.yml runs against the packed .exe:

  {"jsonrpc":"2.0","id":1,"result":{"capabilities":{...},"protocolVersion":"2025-06-18","serverInfo":...
  serverInfo: YES   identity: YES   version 0.0.31: YES
  

• streamable-http boots and honours a custom --host/--port (Uvicorn running on http://127.0.0.1:8931) — the one code path that changed and that neither pytest nor the stdio check touches.
• ruff + mypy + pytest green (79 passed, 2 skipped).

uv.lock re-locked to mcp 2.0.0; CI's --locked sync keeps it honest.

Note

The major-version cap stays, now as mcp>=2,<3. mcp 2.0 arriving unannounced is exactly what broke main in the first place.