[vllm] fix: build_app() missing 1 required positional argument: 'supported_tasks'

[HollowMan6]

Introduced by vllm-project/vllm@76139d0

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Pull request overview

This PR fixes a runtime error where build_app() requires a supported_tasks positional argument in newer versions of vllm. The issue was introduced by vllm commit 76139d0801e95bf6c54352650a6f42e181b510be.

Changes:

• Replaced version-based API compatibility checks with runtime signature inspection for build_app() and init_app_state()
• Added dynamic fetching of supported_tasks from the engine client when required
• Improved robustness by adapting to actual API signatures rather than hardcoded version numbers

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