- Every purge emptied the viewers' RAM preview; Purge ▸ All Disk Cache and Snapshot now leave
it (Image Cache Memory, All Memory, All Memory & Disk Cache, All and All 3D Cache still
clear it).
- The memory purges also drop the decoded footage frames (`FootageSource::purge`, the media
pool's `clear_frames`; decoders stay open), so footage reads decode again.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>