- Remove 35 public container accessors that only tests called (header,
camera/light, keys, footage, masks, shapes, version) and the dead
StyleMap::switch_name. Tests now check the importer's own reading of the
same bytes, or the decoder it uses; three import tests gain the values
the removed checks covered.
- Import and export reports share one loss entry (Loss<C>) with record,
total, count and summary; the JSON shape is pinned for both.
- Collector::lose_with builds a detail only below the detail cap (callers
switch later).
- The export uses the container's TimeBase; one NTSC table serves import
and export; TimeBase::frames saturates like units instead of returning 0.