Egress shim supports the httpx2 lineage (unblocks
anthropic.Anthropic(http_client=egress.client()), which could not work against
the Anthropic SDK 1.x at all) and gains requests_session() for the
requests-based Google client libraries.

New optional extras: httpx2, requests. Core stays zero-dependency.

Note: 0.1.9 was bumped in-repo but never tagged or published; PyPI goes
0.1.8 -> 0.1.10.