Every sheet and dialog barrier goes solid black instead of dimming the
screen behind it whenever dynamic color ("Match wallpaper") is on -
Material 3's ColorScheme.scrim role is fully opaque black by spec,
meant to be used at reduced opacity by whoever paints it, but
NooColors.fromDynamicScheme mapped it straight into barrierColor.
Use the fixed palette's already-translucent scrim instead, matching
how success/warning/info already fall back to it since they have no
dynamic equivalent either.
Also fix the Details sheet's Info/Versions/Activity segmented control
refetching a tab's data every time it's selected: switching on the
active tab picked which single widget to build, so Flutter tore down
and recreated whichever tab wasn't showing on every switch, discarding
its fetched data. Keep all three mounted in an IndexedStack instead
(the same pattern the app's own main tab bar already uses for this
exact reason), so each tab's state - and its one-shot fetch - survives
switching back and forth.