The active photo had a 2 px pure white outline and the other selected photos
grey 170, so on Silver and Paper's light grid the active ring vanished and the
two differed by lightness alone. The loading placeholder was a fixed dark grey
slab in every theme.
- theme.rs: new tokens `ring_active`, `ring_inner`, `ring_selected` and
`placeholder`, per theme; tests that every theme's rings stand 3:1 against
the grid and the square grid's cells, and that the placeholder follows the
theme's family
- panels/grid.rs: `selection_ring` draws the active ring as 3 pt (1 pt inner
line against the photo, 2 pt theme line) and the others as 1.5 pt; the grid
uses it for loaded and unloaded thumbnails, and the placeholder token
- panels/detail.rs: the filmstrip uses the same ring and rule
- panels/compare.rs: the compare placeholder uses the token
- tests_grid.rs, tests_filmstrip.rs: painted ring widths and colours in a
light theme, active versus selected versus unselected
- docs/parity-checklist.md, docs/whats-new.md: rows and entry
Co-Authored-By: Claude <noreply@anthropic.com>
