feat(ui): lower the details hero and make it compact without a backdrop

The stage for a 16:9 backdrop is min(480px, 60vh) instead of 560/72vh,
with the content's top padding at 48px, so the episodes or cast row gains
~80px in a 1200×800 window. A title with only a poster (the common case
on real Xtream and Stalker playlists) gets a compact hero sized by its
content over the blurred poster. The layout is decided once per title: a
backdrop that TMDB enrichment adds a moment later fills the compact hero
instead of growing it under the cursor.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

docs/architecture/iptvnator-ui-guidelines.md

@@ -158,9 +158,13 @@ VOD and series detail screens share `app-portal-detail-shell` and
 kind label ("Movie · playlist") → title → chips → description (three lines,
 "More") → resume bar → action row → credits, with the poster bottom-aligned
 on the left and the backdrop filling the hero behind a two-layer scrim built
-from `--app-content-bg`. Without a backdrop, or when the provider sends the
-poster as the backdrop, the blurred poster fills the stage. The pane is a
-size container (`detail`); the poster hides below 760px of pane width.
+from `--app-content-bg`. The hero keeps `min(480px, 60vh)` of stage for a
+16:9 backdrop. Without one, or when the provider sends the poster as the
+backdrop, the hero is compact (`hero--compact`, sized by its content) over
+the blurred poster. The layout is decided once per title, so a backdrop that
+TMDB enrichment adds a moment later fills the compact hero instead of
+growing it. The pane is a size container (`detail`); the poster hides below
+760px of pane width.
 
 The pieces are shared and provider-neutral (`libs/ui/components/src/lib/detail-ui/`):
 `app-meta-chip` (pill; `rating` and `status` variants; facets as projected