Support mcp SDK 2.0, which renamed FastMCP to MCPServer

[erikgaas]

Fixes #21. The MCP python SDK 2.0.0 (released 2026-07-28 alongside the new spec) renamed FastMCP to MCPServer and moved it to mcp.server.mcpserver, so clikernel-mcp fails at import on any environment resolving the unpinned mcp dep to 2.x (hit in the wild on a solveit instance image built after the release). Everything else clikernel uses (run_stdio_async, tool(structured_output=...), the instructions= kwarg) is unchanged in 2.0.0, so the fix is a dual import (2.x path first, 1.x fallback; the alias keeps the diff minimal) plus flooring the dep at mcp>=1.2 so pre-FastMCP versions fail at resolve time instead of import time.

Verification: red-green against real mcp 2.0.0 in a clean venv (reproduced the exact ModuleNotFoundError, then a v2 ClientSession over stdio: all three tools listed, state persists across execute calls); the same client test passes on mcp 1.29.0 via the fallback branch; pytest tests -q 24/24 after rebasing onto current main.

An earlier revision of this PR also migrated llmsurgery.dlgskill imports to aidialog (#22), but current main already has that change, so the PR is rebased down to the mcp fix only.