feat(mcp): port the server to MCP Python SDK v2 (FastMCP → MCPServer) (#2196)

- server.py: `mcp.server.mcpserver.MCPServer`; StrictArgsFastMCP becomes
  StrictArgsMCPServer, whose call_tool takes and forwards v2's `context`
  and raises ToolError (the SDK logs anything else as an unexpected crash;
  the message reaches the caller either way).
- stateless_http and transport_security moved from the constructor to
  `streamable_http_app(...)` in mount_mcp, with their reasons.
- Per-request user identity is unchanged: the contextvar set around the
  ASGI call reaches the handler on both v2 paths (legacy stateless spawns
  from the request task; the 2026-07-28 modern path opens its task group
  inside the request).
- pyproject: mcp[cli]>=2.2, no ceiling (installs are --locked). uv.lock
  regenerated with --upgrade-package mcp in the ci-python image: only mcp
  and its own dependencies moved (106 → 110 packages).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_mcp_strict_args.py

@@ -1,23 +1,24 @@
 """Unknown tool arguments are rejected, never silently dropped (#2709).
 
-The failure this pins: FastMCP validates tool arguments with a pydantic model
+The failure this pins: MCPServer validates tool arguments with a pydantic model
 whose extra-field policy is "ignore", so `create_note(content=...)` — a
 plausible near-miss for `body=`, primed by add_task_log's `content` — ran
 successfully, stored `body: ""`, and left a record embedding/search cannot
 see. The call REPORTED SUCCESS. Two real notes were persisted body-less
 before the pattern was noticed.
 
-The fix is at the dispatch seam, not per-tool: StrictArgsFastMCP rejects any
+The fix is at the dispatch seam, not per-tool: StrictArgsMCPServer rejects any
 call carrying arguments the tool does not declare, with a did-you-mean when
 one is close. An error the caller sees once beats data half-written forever.
 """
 import pytest
+from mcp.server.mcpserver.exceptions import ToolError
 
-from scribe.mcp.server import StrictArgsFastMCP
+from scribe.mcp.server import StrictArgsMCPServer
 
 
-def _echo_server() -> StrictArgsFastMCP:
-    mcp = StrictArgsFastMCP("strict-test")
+def _echo_server() -> StrictArgsMCPServer:
+    mcp = StrictArgsMCPServer("strict-test")
 
     @mcp.tool()
     def echo(text: str = "") -> str:
@@ -36,7 +37,7 @@ async def test_unknown_argument_is_an_error_not_a_silent_drop():
     """The load-bearing property: the call must FAIL, because succeeding is
     what turned a typo into data loss."""
     mcp = _echo_server()
-    with pytest.raises(ValueError) as exc:
+    with pytest.raises(ToolError) as exc:
         await mcp.call_tool("echo", {"txt": "hi"})
     msg = str(exc.value)
     assert "'txt'" in msg
@@ -51,7 +52,7 @@ async def test_empty_arguments_pass():
 
 async def test_unknown_tool_keeps_the_upstream_error():
     """The gate must not swallow or reshape 'no such tool' — that error path
-    belongs to FastMCP and clients already understand it."""
+    belongs to MCPServer and clients already understand it."""
     mcp = _echo_server()
     with pytest.raises(Exception) as exc:
         await mcp.call_tool("no_such_tool", {"text": "hi"})
@@ -65,8 +66,8 @@ async def test_the_original_regression_create_note_with_content():
     from scribe.mcp.server import build_mcp_server
 
     mcp = build_mcp_server()
-    assert isinstance(mcp, StrictArgsFastMCP)   # the guard is actually mounted
-    with pytest.raises(ValueError) as exc:
+    assert isinstance(mcp, StrictArgsMCPServer)   # the guard is actually mounted
+    with pytest.raises(ToolError) as exc:
         await mcp.call_tool(
             "create_note", {"title": "t", "content": "the body text"}
         )