feat(video): add Dreamina CLI provider tool for Seedance 2.0

[STEPHENXING]

Summary

• Add \DreaminaCliVideo\ (\ ools/video/dreamina_cli_video.py) backing \ ext2video, \image2video, \rames2video, and \multimodal2video\ (Seedance 2.0).
• Zero-overhead discovery: silently stays \UNAVAILABLE\ if \dreamina\ CLI is missing; probes \user_credit\ only when binary exists.
• Async \submit_id\ + \query_result\ polling with UTF-8 encoding protection on Windows.
• Add contract tests (\ ests/contracts/test_dreamina_cli_video.py, 9/9 passed).

Verification

• Ran 9/9 unit contract tests (\pytest tests/contracts/test_dreamina_cli_video.py).
• Verified zero-overhead painless discovery when \dreamina\ CLI is missing.
• Verified real end-to-end task submission and video generation.