Add VLLMOpenAIModelClass parent class with cancellation support and health probes

[christineyu123]

Summary

• Adds VLLMOpenAIModelClass (clarifai/runners/models/vllm_openai_class.py) — a parent class that vLLM model implementations can subclass instead of writing a standalone model.py from scratch. Subclasses only need to implement load_model() to set self.server, self.client, self.model, and self.cancellation_handler.
• Adds VLLMCancellationHandler — manages per-request cancellation via register_item_abort_callback. When the Clarifai runtime signals an abort, it sets a threading.Event and closes the underlying httpx response, causing vLLM to detect is_disconnected(), abort the engine, and free KV cache.
• openai_stream_transport in VLLMOpenAIModelClass handles both /chat/completions and /responses endpoints with full cancellation support (including the race condition where abort arrives before the stream starts).
• handle_liveness_probe / handle_readiness_probe hit vLLM's /health endpoint directly when a server is running; fall back to the base class behaviour when no server is set.
• Adds tests/runners/test_vllm_openai_class.py with 17 unit tests covering VLLMCancellationHandler state transitions, health probe delegation, and streaming cancellation behaviour — no real vLLM process required.

Test plan

• All 17 new unit tests pass locally (uv run pytest tests/runners/test_vllm_openai_class.py -v)
• CI green on all matrix targets (macOS/Ubuntu/Windows × Python 3.11/3.12)
• Manual smoke-test: subclass VLLMOpenAIModelClass in a model upload (e.g. trinity-mini-thinking-vllm) and verify abort cancels the running generation

🤖 Generated with Claude Code

[github-actions]

Package	Line Rate	Health
clarifai	45%	❌
clarifai.cli	62%	➖
clarifai.cli.templates	67%	➖
clarifai.cli.templates.toolkits	100%	✔
clarifai.client	65%	➖
clarifai.client.auth	67%	➖
clarifai.constants	100%	✔
clarifai.datasets	100%	✔
clarifai.datasets.export	69%	➖
clarifai.datasets.upload	75%	➖
clarifai.datasets.upload.loaders	37%	❌
clarifai.models	100%	✔
clarifai.rag	0%	❌
clarifai.runners	52%	➖
clarifai.runners.models	59%	➖
clarifai.runners.pipeline_steps	39%	❌
clarifai.runners.pipelines	72%	➖
clarifai.runners.utils	62%	➖
clarifai.runners.utils.data_types	72%	➖
clarifai.schema	100%	✔
clarifai.urls	58%	➖
clarifai.utils	65%	➖
clarifai.utils.evaluation	16%	❌
clarifai.workflows	95%	✔
Summary	60% (11553 / 19181)	➖

Minimum allowed line rate is 50%

[ackizilkale]

Looks good!