The initialize handshake is negotiated by the SDK with no knowledge of the
server's protocol_versions allowlist, and FastMCP can only veto the handshake,
not steer the negotiated revision. So a server pinned to an older handshake
revision (e.g. ["2024-11-05"]) wrongly refused an ordinary client that
requested a newer handshake revision. Enforce era membership for handshake
versions (exact membership stays for modern per-request versions), refusing
only a genuine cross-era mismatch.
Replace `min_protocol_version` with `protocol_versions`, an allowlist of MCP
protocol versions taking the SDK's own era tuples. Versions are an enumerated
set, not an ordered scalar, so enforcement is set membership rather than a
bound -- which is what makes handshake-only expressible.
Generalize the startup coherence check into a capability -> required-versions
map, and make it silent unless a version set was declared.
