Port to the mcp 2.x SDK (co-install with pmcp 3) #124

Published index-it-mcp 1.4.1 and 1.5.0 require mcp>=1.0.0 with no upper bound. A plain pip install index-it-mcp therefore resolves mcp 2.3.0, and index-it-mcp stdio crashes at import:

ImportError: cannot import name 'McpError' from 'mcp.shared.exceptions' (Did you mean: 'MCPError'?)

The release smoke and the PMCP pilot both install with the repo's lock constraints (mcp 1.27.0), so neither caught this. The corrective 1.5.1 caps mcp<2.

That cap means index-it-mcp can't share an environment with pmcp 3.x, which requires mcp>=2.2,<3.

Scope (target 1.6.0)

• Port mcp_server to the mcp 2.x SDK: the McpError→MCPError rename and any other 2.0–2.3 API changes in the server, STDIO transport, client and tests.
• Set the requirement to mcp>=2.2,<3 and refresh uv.lock.
• The release smoke must also install the wheel without lock constraints, so an unbounded or too-loose dependency can't hide again.
• Acceptance: CI is green on Python 3.12, 3.13 and 3.14. The wheel co-installs with both phase-loop-runtime==0.7.30 and pmcp 3.x with a clean uv pip check, and the STDIO server starts and serves queries.