Third theme-aware v1 (after add_modal_shell_v1 and add_toast_v1).
Same dashed-border "no data yet" tile shape as v0 with a `theme`
param that swaps 5 colors (bg / border / icon / title / subtitle):
- light (default): byte-parity with v0 (slate-50 / slate-300)
- dark: slate-800 bg + slate-600 border + slate-200 title
- system: $color-surface-2 / $color-border / $color-text-primary
refs — requires applySemanticPalette(doc) seeded
Lets dark-theme dashboards keep a matching empty-slot surface
instead of punching a light rectangle out of dark cards.
d1022e74d5