[ankit-v2-3]

Summary

Adds 3D .cube LUT colour grading to the editor, matching the server-side contract in Spext/streaming_service#75 and Spext/videodb-server#1052.

• Lut(src, intensity=1.0): src is the URL of a .cube file; intensity blends from untouched (0) to fully graded (1).
• Lut.from_file(connection, path, intensity) uploads a local .cube through the collection upload URL (the same upload_bytes path large timelines use) and returns a Lut pointing at it. The server rewrites that upload URL to a readable one before compile.
• Clip(lut=...) grades one clip, applied before its filter. Not valid on audio or caption clips (the server rejects it).
• Timeline.lut grades the whole composited frame, under any captions.
• Both are emitted only when set, like filter, so existing timelines serialize exactly as before. Older servers ignore the field silently, so deploy the service first.

timeline = Timeline(conn)
timeline.lut = Lut.from_file(conn, "teal-orange.cube", intensity=0.8)
track.add_clip(0, Clip(asset=VideoAsset(id=video.id), duration=10, lut=Lut(src=url), filter=Filter.contrast))

Test plan

• pytest — 11 passed (6 new in tests/test_editor_lut.py: serialization, intensity bounds, emit-only-when-set on Clip and Timeline, from_file upload call and error wrapping)
• Against a dev deployment of the two server PRs: generate_stream() on a timeline with a clip LUT and a timeline LUT, confirm the graded stream plays

🤖 Generated with Claude Code

[ankit-v2-3]

Superseded by #110: the branch was renamed to ankit/editor-lut-motion and now carries both the LUT and motion changes. GitHub closed this PR on the rename (head ref deleted) and it cannot be reopened.