v3.4.7

C++ port tracking the upstream fastmcp v3.4.7 stable line.

Upstream parity (fastmcp v3.4.4 → v3.4.7)

• Deterministic required ordering in transformed tools — the transformed-tool schema now emits required in a stable order instead of hash/bucket order (upstream fastmcp PR 4564).
• OpenAPI deepObject query serialization — object query parameters declared with style: deepObject now serialize as param[prop]=value instead of bare prop=value (upstream fastmcp PR 4523).

Fixes

• arguments._meta no longer stripped in the sampling tool-call path (#47). The sampling-enabled tools/call handler previously replaced the whole _meta object with just session_id, dropping every client-provided member. It now preserves the full _meta and only adds session_id. Thanks to @yuz1 for the report. A regression test (tests/mcp/test_meta_passthrough.cpp) guards it.

Verification

Full unit suite (116/116) and cross-implementation interop with the Python reference (253/253) green.