Detail the WebSocket API surface in the 2.6.0 and 2.7.0 changelogs

[Kludex]

Summary

Follow-up to #1080, cross-checked against the GitHub release notes and the public API diffs between tags:

• 2.7.0 was under-reported: the httpx-ws v0.9.0 sync (Update vendored httpx-ws to upstream v0.9.0 #1067) also added WebSocketClient and AsyncWebSocketClient to httpx2.websockets - new public API, now listed under Added. The Changed entry also mentions the previous vendored snapshot was outdated, matching the release notes.
• 2.6.0: the WebSocket entry now names the actual surface (client.websocket(), httpx2.websocket(), the httpx2.websockets module), and the QUERY entry mentions the CLI support.

For the record, #983 and #1045 from the v2.6.0 release notes are intentionally in the httpcore2 changelog, following the per-package split.

AI Disclaimer

This PR was developed with the assistance of either Claude or Codex. I've reviewed and verified the changes.

[github-actions]

Docs preview: https://f873de89-httpx2-docs.pydantic.workers.dev

[codspeed-hq]

Merging this PR will not alter performance

✅ 15 untouched benchmarks
⏩ 7 skipped benchmarks¹

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_{Comparing changelog-ws-details (4244efc) with main (c6028d9)}

Footnotes

1. 7 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩