Notification taps for post-related types (REACTION/COMMENT/MENTION/
PAW_BACK) landed on a bare "no comments yet" screen with no sign of the
actual post. The comments screen now fetches the post via the existing
posts.getById and shows it (image/caption/header) via the shared
PostCard above the comment list.
The actor's name in each notification row is now its own tappable text
run that links to their profile, separate from tapping the rest of the
row (which still opens the notification's target) — ported from web's
notifications page, which does the same split between a Link and plain
text.
Also fixed: the comments screen used the static (light-only) color
tokens throughout, so embedding the theme-aware PostCard produced
near-invisible light text on its own light background in dark mode.
Converted the screen to useTheme() like the rest of the dark-mode-
converted screens.