feat: add SiftQ H3 video at $0.015/sec (768P) and $0.025/sec (2K)

[futurestudyspace]

Summary

Add an independent SiftQ provider for MiniMax-H3 V2-compatible video generation.

SiftQ offers the lowest-priced H3 route currently documented in OpenMontage: $0.015/sec at 768P and $0.025/sec at 2K. A 15-second 2K generation is estimated at $0.375.

The provider has its own identity, API key, base URL, request mapper, polling flow, error handling, documentation, and tests. It does not import, wrap, or rename the existing MiniMax provider.

Related issue

N/A — no issue was opened because this is a focused provider integration and the contribution rules do not require a prior issue.

Changes

• add the auto-discovered siftq_video provider using SIFTQ_API_KEY
• use https://siftq.com/api/minimax/ as the default compatible V2 endpoint
• support text-to-video, image-to-video, first/last-frame, and mixed image/video/audio reference generation
• validate prompts, duration, resolution, ratios, media types, media limits, and request size
• add bounded asynchronous polling, structured error mapping, safe retries, output validation, and secret redaction
• add usage-aware cost reporting:
  • 768P video: $0.015/sec
  • 2K video: $0.025/sec
  • reference video: same per-second rate as the selected output resolution
  • reference images: first 5 included, then $0.008/image
  • audio input: free
• expose first_last_frame_to_video through video_selector
• add SiftQ environment configuration, provider documentation, README coverage, and a Layer 3 provider skill
• add positive, negative, boundary, routing, pricing, and secret-isolation tests

Testing

• provider, selector, adjacent-provider, and related contract tests: 377 passed
• Python AST and compile checks: passed
• pip check: no broken requirements
• git diff --check: passed
• secret and reference-provider scans: passed
• GitHub commit signature: verified and valid

A live paid API request was not run because no runtime SIFTQ_API_KEY was available in the implementation environment.

Out of scope

OpenMontage does not currently expose task listing, cancellation, callbacks, or H3 Context IR through its public video tool contract, so this provider does not advertise those capabilities.

Checklist

• The change is focused on a single logical concern.
• I ran the relevant tests locally.
• I updated docs/README for the new behavior and configuration.
• No unrelated build artifacts or local configuration are included.