HF_RUNTIME_FIX_RECEIPT_6.md

# HF Runtime Fix Receipt 6 — PATCHED8 Preview Rehydration

## Status
HELD for preview-repair packet generation.

## Fault observed
The app route processed the video and generated trace receipts, but both top video preview panes showed blank/NaN preview behavior in the Gradio UI.

## Cause class
Gradio `Video` upload/preview behavior was unreliable for this Space runtime even though the uploaded video was readable by OpenCV and the route completed.

## Patch applied
- Replaced the left upload `gr.Video` control with a `gr.File` video uploader so file intake is stable and path-bound.
- Added `coerce_uploaded_path()` to support Gradio file/video payload variants.
- Added `make_preview_mp4()` to create a browser-stable MP4 preview without mutating the canonical source video.
- Added upload-time preview rehydration via `video_input.change(...)`.
- Returned the browser-safe preview MP4 after route execution instead of returning the raw uploaded path.
- Kept source hashing, atomization, frame extraction, scene detection, trace-stack construction, receipt generation, and packet creation intact.

## Boundary preserved
The preview MP4 is a display artifact only. The canonical source remains the uploaded video hash and source capsule authority.

## Expected result
After upload, the right preview pane should populate with a playable browser-safe MP4. After route execution, the same preview pane should remain populated while receipts/tables/gallery are generated.