ci(examples): cover openai_websocket_client and openresponses_client

[chaliy]

What

Add the two remaining examples/ scripts that the Examples CI job was not running:

• examples/openai_websocket_client.py — exercises the WebSocket mode for the OpenAI Responses API (added in feat(api): add WebSocket mode for Responses API #26).
• examples/openresponses_client.py — exercises the OpenResponses API at /openresponses/v1/responses.

Why

Routine maintenance spec R3.2/R4.2 expects integration coverage of every API surface. The Rust examples and most Python clients are run in CI today, but these two surfaces were only covered by hand-runs — any API drift in WebSocket or OpenResponses would surface as a user-reported breakage rather than a red build.

How

Both new steps reuse the release server already started by the existing job (./target/release/llmsim serve --port 8080). Each example is a self-contained uv run script that exits cleanly on success.

I smoke-tested both scripts locally against the running server before adding them:

• openresponses_client.py walks text input, message input, streaming, and 3 different models.
• openai_websocket_client.py exercises text input, message-array input, and multi-turn previous_response_id.

Risk

• Low. Two additive CI steps. If a regression breaks WebSocket or OpenResponses streaming, CI will now catch it; no change to runtime code.

Checklist

• Both scripts ran cleanly against the freshly built release server
• CI job step ordering preserved (run after Start server)