release: Buddy2api v2.1.1 reasoning effort compatibility

[wicm84266964]

Change

Add cross-agent reasoning-effort compatibility for Chat Completions and Responses, including common OpenCode, DSH, Cherry, and Claude-style request forms.

• Normalize reasoning controls across WorkBuddy, QClaw, and QwenWork while documenting TraeWork's current limitation.
• Route /v1/responses through the API key's bound provider.
• Emit standard Responses reasoning summary events and support reasoning-only completions.
• Set WorkBuddy DeepSeek V4 Pro/Flash default reasoning to high, with an environment switch to disable it.
• Prepare the v2.1.1 version metadata and release notes.

Validation

• I ran the repository's documented local checks: python -m compileall -q . and python -m pytest -q (238 passed).
• I rebuilt and restarted the Docker service; /health reports 2.1.1 and the container is healthy.
• I did not add credentials, databases, private account data, or runtime output.
• I reviewed the changed-file list.
• I will wait for every required CI check before merging.
• I did not create or move a release tag in this pull request.