v1.12.0-rc.2

Changes since v1.12.0-rc.1

• fix(export): take the output shape from the scene, never a hardcoded 16:9
• fix(timeline): stop losing the source-dimension backfill on fresh recordings
• test(timeline): cover the backfill retry after a timed-out save wait

Full Changelog: v1.12.0-rc.1...v1.12.0-rc.2