- A watch-folder render gives the host session's set back after its own
project replaced it on the shared footage source.
- Guard gpu fx_depth::IDS against reads_aux drifting apart.
- Count picture and channel decodes per thread instead of reading the
shared channel cache, so parallel tests can't make the checks flaky.
- The engine test fails when no set was ever sent.
- Docs: Media Replacement items are learned at their first frame.
Refs #474
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>