fix(sheets): size sheets to their content instead of 75% of the window

Sheets rendered at the host's maximum height regardless of content, so a
one-item player queue or a two-track picker filled ~75% of a desktop window
with empty space.

BottomSheetPageScaffold now always lays out Column(mainAxisSize: .min) plus
Flexible(child:), and each sheet body shrink-wraps its own scrollable. The
scaffold's shrinkWrap flag is gone: its old true branch put the child on an
unbounded axis, where an over-tall list overflowed instead of clamping and
scrolling. Measured on a 1600x1000 window, the chapter sheet goes from 750px
to 118px for one chapter and the two-column track sheet from 750px to 154px
for one audio and one subtitle track, both still clamping at the cap.

Add SheetSplitColumns for the three side-by-side sheet layouts. A bare
VerticalDivider has no intrinsic height, so it inflated those rows to the cap
on its own; the rule now paints from a Positioned.fill that cannot size the
Stack. IntrinsicHeight is not an option because a Viewport has no intrinsics.

Because sheets are bottom-anchored, a content-driven height moves the sheet's
top edge and everything above the change point. Three surfaces opt out for
that reason and say so at the call site: SubtitleSearchSheet and its language
picker keep filling, since both refilter under an autofocused field;
FiltersBottomSheet holds the outgoing page's height through its loading
transient; and RatingBottomSheet no longer hides MAL/AniList rows
asynchronously, which used to slide live rating controls down two rows several
hundred ms after open. Wrap the shared StateMessageWidget at the filters sheet
boundary rather than editing a widget with 33 filling call sites.

The host gains an AnimatedSize keyed per sheet session so nested pushes ease
while a replacing show adopts its own height, a 720px absolute height ceiling
on desktop windows only, and a min(max(25%, 96px), 60%) drag-dismiss threshold
so short sheets neither close on a nudge nor become undismissable.

Add videoControls.noAudioDevicesAvailable so the audio output page shows a
placeholder instead of a bare header while devices load.

lib/i18n/strings_en.g.dart

@@ -2026,6 +2026,9 @@ class Translations$videoControls$en {
 	/// en: 'No items in queue'
 	String get noQueueItems => 'No items in queue';
 
+	/// en: 'No audio devices available'
+	String get noAudioDevicesAvailable => 'No audio devices available';
+
 	/// en: 'Search Subtitles'
 	String get searchSubtitles => 'Search Subtitles';
 
@@ -6758,6 +6761,7 @@ extension on Translations {
 			'videoControls.noChaptersAvailable' => 'No chapters available',
 			'videoControls.queue' => 'Queue',
 			'videoControls.noQueueItems' => 'No items in queue',
+			'videoControls.noAudioDevicesAvailable' => 'No audio devices available',
 			'videoControls.searchSubtitles' => 'Search Subtitles',
 			'videoControls.language' => 'Language',
 			'videoControls.noSubtitlesFound' => 'No subtitles found',
@@ -7143,9 +7147,9 @@ extension on Translations {
 			'explore.badge.requested' => 'Requested',
 			'explore.badge.pendingApproval' => 'Pending approval',
 			'explore.badge.processing' => 'Processing',
-			'explore.badge.declined' => 'Declined',
 			_ => null,
 		} ?? switch (path) {
+			'explore.badge.declined' => 'Declined',
 			'explore.badge.requestFailed' => 'Request failed',
 			'explore.badge.requested4k' => '4K requested',
 			'explore.badge.seasonsAvailable' => ({required Object available, required Object total}) => '${available}/${total} seasons',
@@ -7657,9 +7661,9 @@ extension on Translations {
 			'performanceOverlay.dropped' => 'Dropped',
 			'performanceOverlay.dvRpus' => 'DV RPUs',
 			'performanceOverlay.dvRpuAverage' => 'DV RPU Avg',
-			'performanceOverlay.dvSampleAverage' => 'DV Sample Avg',
 			_ => null,
 		} ?? switch (path) {
+			'performanceOverlay.dvSampleAverage' => 'DV Sample Avg',
 			'performanceOverlay.maxLuma' => 'Max Luma',
 			'performanceOverlay.minLuma' => 'Min Luma',
 			'performanceOverlay.maxCll' => 'MaxCLL',