Tags: 0xeb/fastmcpp

release: fastmcpp v3.4.7 — upstream parity + _meta passthrough fix

Sync from the private v3.4.7 line.

Upstream fastmcp v3.4.4 -> v3.4.7 parity:
- Deterministic `required` ordering in transformed tools (fastmcp PR 4564).
- OpenAPI deepObject query-parameter serialization (fastmcp PR 4523).

Fix: the sampling tools/call handler replaced `arguments._meta` with just
`{session_id}`, dropping every client-provided member. It now preserves the
full `_meta` and only adds session_id. Regression test included.

Fixes #47.