feat(mobile): add selectable Pocket model size

mobile/integration_test/pocket_voice_integration_test.dart

@@ -1,6 +1,7 @@
 import 'dart:io';
 
 import 'package:buzz/shared/voice/pocket_model_downloader.dart';
+import 'package:buzz/shared/voice/pocket_model_manifest.dart';
 import 'package:buzz/shared/voice/pocket_voice_worker.dart';
 import 'package:buzz/shared/voice/voice_audio_output.dart';
 import 'package:flutter/foundation.dart';
@@ -16,12 +17,17 @@ void main() {
       const configuredModelPath = String.fromEnvironment(
         'BUZZ_POCKET_MODEL_DIR',
       );
+      const configuredPrecision = String.fromEnvironment(
+        'BUZZ_POCKET_PRECISION',
+        defaultValue: 'fp32',
+      );
+      final variant = PocketModelVariant.fromStored(configuredPrecision);
       const downloadModel = bool.fromEnvironment('BUZZ_POCKET_DOWNLOAD');
       var modelPath = configuredModelPath;
       Duration? downloadTime;
       if (modelPath.isEmpty && downloadModel) {
         final clock = Stopwatch()..start();
-        final downloader = PocketModelDownloader();
+        final downloader = PocketModelDownloader(variant: variant);
         final directory = await downloader.install((downloaded, total, file) {
           if (downloaded == total) {
             debugPrint('Pocket model download complete: $file ($total bytes)');
@@ -40,7 +46,9 @@ void main() {
       }
 
       final worker = PocketVoiceWorker();
-      await worker.start(modelPath);
+      final loadClock = Stopwatch()..start();
+      await worker.start(modelPath, precision: variant.nativePrecision);
+      loadClock.stop();
       addTearDown(worker.dispose);
 
       final firstClock = Stopwatch()..start();
@@ -128,6 +136,8 @@ void main() {
       // Emitted in a stable shape so simulator/device runs are easy to compare.
       debugPrint(
         'BUZZ_POCKET_METRICS '
+        'precision=${variant.precision} '
+        'load_ms=${loadClock.elapsedMilliseconds} '
         'first_pcm_ms=${firstClock.elapsedMilliseconds} '
         'ttfap_ms=${firstPlaybackClock.elapsedMilliseconds} '
         'synthesis_ms=${first.synthesisTime.inMilliseconds} '

mobile/lib/features/settings/settings_page.dart

@@ -1,3 +1,5 @@
+import 'dart:async';
+
 import 'package:flutter/material.dart';
 import 'package:flutter_hooks/flutter_hooks.dart';
 import 'package:hooks_riverpod/hooks_riverpod.dart';
@@ -11,6 +13,7 @@ import '../../shared/relay/relay.dart';
 import '../../shared/theme/theme.dart';
 import '../../shared/voice/pocket_model_manifest.dart';
 import '../../shared/voice/pocket_model_provider.dart';
+import '../../shared/voice/pocket_voice_controller.dart';
 import '../../shared/widgets/app_list.dart';
 import '../../shared/widgets/app_list_card.dart';
 import '../../shared/widgets/frosted_app_bar.dart';

mobile/lib/features/settings/settings_page/voice_section.dart

@@ -7,6 +7,10 @@ class _VoiceSection extends ConsumerWidget {
   Widget build(BuildContext context, WidgetRef ref) {
     final model = ref.watch(pocketModelProvider);
     final downloading = model.phase == PocketModelPhase.downloading;
+    final switching =
+        downloading ||
+        model.phase == PocketModelPhase.checking ||
+        model.phase == PocketModelPhase.verifying;
     final status = switch (model.phase) {
       PocketModelPhase.checking => 'Checking…',
       PocketModelPhase.absent => 'Not downloaded',
@@ -30,13 +34,26 @@ class _VoiceSection extends ConsumerWidget {
     return AppListCard(
       label: 'Voice',
       children: [
+        AppListRow(
+          icon: LucideIcons.gauge,
+          title: 'Model size',
+          subtitle: model.variant == PocketModelVariant.higherQuality
+              ? 'Best voice quality. Uses more storage and memory.'
+              : 'Smaller and faster. Uses the supported hybrid INT8 model.',
+          subtitleMaxLines: 2,
+          value: model.variant.label,
+          trailing: switching ? null : const _RowChevron(),
+          onTap: switching
+              ? null
+              : () => _showModelSizePicker(context, ref, model.variant),
+        ),
         AppListRow(
           icon: LucideIcons.audioLines,
           title: 'Pocket voice',
           subtitle:
               model.message ??
               'Private, on-device speech. Downloads '
-                  '${pocketModelRuntimeBytes ~/ 1000000} MB after install.',
+                  '${model.variant.runtimeBytes ~/ 1000000} MB after install.',
           subtitleMaxLines: 3,
           value: status,
           trailing: downloading
@@ -56,14 +73,58 @@ class _VoiceSection extends ConsumerWidget {
                 ),
           onTap: action,
         ),
-        const AppListRow(
+        AppListRow(
           icon: LucideIcons.hardDriveDownload,
           title: 'Model storage',
-          value: '${pocketModelRuntimeBytes ~/ 1000000} MB',
+          value: '${model.variant.runtimeBytes ~/ 1000000} MB',
           subtitle: 'Stored in application support, not duplicated in assets.',
           subtitleMaxLines: 2,
         ),
       ],
     );
   }
 }
+
+Future<void> _showModelSizePicker(
+  BuildContext context,
+  WidgetRef ref,
+  PocketModelVariant selected,
+) => showModalBottomSheet<void>(
+  context: context,
+  showDragHandle: true,
+  builder: (context) => SafeArea(
+    child: Column(
+      mainAxisSize: MainAxisSize.min,
+      children: [
+        for (final variant in PocketModelVariant.values)
+          ListTile(
+            leading: Icon(
+              variant == selected
+                  ? LucideIcons.circleCheck
+                  : LucideIcons.circle,
+            ),
+            title: Text(variant.label),
+            subtitle: Text(
+              variant == PocketModelVariant.higherQuality
+                  ? 'FP32 · ${variant.runtimeBytes ~/ 1000000} MB'
+                  : 'Hybrid INT8 · ${variant.runtimeBytes ~/ 1000000} MB',
+            ),
+            onTap: () {
+              Navigator.pop(context);
+              unawaited(_selectPocketModelVariant(ref, variant));
+            },
+          ),
+        const SizedBox(height: Grid.xs),
+      ],
+    ),
+  ),
+);
+
+Future<void> _selectPocketModelVariant(
+  WidgetRef ref,
+  PocketModelVariant variant,
+) async {
+  if (variant == ref.read(pocketModelProvider).variant) return;
+  await ref.read(pocketVoiceProvider.notifier).releaseEngineForModelSelection();
+  await ref.read(pocketModelProvider.notifier).select(variant);
+}