Add version control to track editor, restyle story list

- Story items can be pinned to a specific generation version via
  toolbar dropdown (shows when clip is selected and has >1 version)
- version_id column on story_items with migration, validated against
  the generation's versions before saving
- Split/duplicate preserve the source clip's pinned version
- Export and playback resolve version-specific audio paths
- Extracted _build_item_detail helper in stories.py (DRY cleanup)
- Story list restyled from rounded cards to flat rows with rounded
  hover/active states, gradient header fade, and dynamic bottom
  padding that accounts for track editor + generate box

app/src/lib/api/client.ts

@@ -27,6 +27,7 @@ import type {
   StoryItemReorder,
   StoryItemSplit,
   StoryItemTrim,
+  StoryItemVersionUpdate,
   StoryResponse,
   TranscriptionResponse,
   VoiceProfileCreate,
@@ -588,6 +589,17 @@ class ApiClient {
     });
   }
 
+  async setStoryItemVersion(
+    storyId: string,
+    itemId: string,
+    data: StoryItemVersionUpdate,
+  ): Promise<StoryItemDetail> {
+    return this.request<StoryItemDetail>(`/stories/${storyId}/items/${itemId}/version`, {
+      method: 'PUT',
+      body: JSON.stringify(data),
+    });
+  }
+
   async exportStoryAudio(storyId: string): Promise<Blob> {
     const url = `${this.getBaseUrl()}/stories/${storyId}/export-audio`;
     const response = await fetch(url);

app/src/lib/api/types.ts

@@ -222,6 +222,7 @@ export interface StoryItemDetail {
   id: string;
   story_id: string;
   generation_id: string;
+  version_id?: string;
   start_time_ms: number;
   track: number;
   trim_start_ms: number;
@@ -236,6 +237,12 @@ export interface StoryItemDetail {
   seed?: number;
   instruct?: string;
   generation_created_at: string;
+  versions?: GenerationVersionResponse[];
+  active_version_id?: string;
+}
+
+export interface StoryItemVersionUpdate {
+  version_id: string | null;
 }
 
 export interface StoryDetailResponse {

app/src/lib/hooks/useStories.ts

@@ -1,6 +1,15 @@
 import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query';
 import { apiClient } from '@/lib/api/client';
-import type { StoryCreate, StoryItemCreate, StoryItemBatchUpdate, StoryItemReorder, StoryItemMove, StoryItemTrim, StoryItemSplit } from '@/lib/api/types';
+import type {
+  StoryCreate,
+  StoryItemBatchUpdate,
+  StoryItemCreate,
+  StoryItemMove,
+  StoryItemReorder,
+  StoryItemSplit,
+  StoryItemTrim,
+  StoryItemVersionUpdate,
+} from '@/lib/api/types';
 import { usePlatform } from '@/platform/PlatformContext';
 
 export function useStories() {
@@ -109,8 +118,15 @@ export function useMoveStoryItem() {
   const queryClient = useQueryClient();
 
   return useMutation({
-    mutationFn: ({ storyId, itemId, data }: { storyId: string; itemId: string; data: StoryItemMove }) =>
-      apiClient.moveStoryItem(storyId, itemId, data),
+    mutationFn: ({
+      storyId,
+      itemId,
+      data,
+    }: {
+      storyId: string;
+      itemId: string;
+      data: StoryItemMove;
+    }) => apiClient.moveStoryItem(storyId, itemId, data),
     onSuccess: (_, variables) => {
       queryClient.invalidateQueries({ queryKey: ['stories'] });
       queryClient.invalidateQueries({ queryKey: ['stories', variables.storyId] });
@@ -122,8 +138,15 @@ export function useTrimStoryItem() {
   const queryClient = useQueryClient();
 
   return useMutation({
-    mutationFn: ({ storyId, itemId, data }: { storyId: string; itemId: string; data: StoryItemTrim }) =>
-      apiClient.trimStoryItem(storyId, itemId, data),
+    mutationFn: ({
+      storyId,
+      itemId,
+      data,
+    }: {
+      storyId: string;
+      itemId: string;
+      data: StoryItemTrim;
+    }) => apiClient.trimStoryItem(storyId, itemId, data),
     onSuccess: (_, variables) => {
       queryClient.invalidateQueries({ queryKey: ['stories'] });
       queryClient.invalidateQueries({ queryKey: ['stories', variables.storyId] });
@@ -135,8 +158,15 @@ export function useSplitStoryItem() {
   const queryClient = useQueryClient();
 
   return useMutation({
-    mutationFn: ({ storyId, itemId, data }: { storyId: string; itemId: string; data: StoryItemSplit }) =>
-      apiClient.splitStoryItem(storyId, itemId, data),
+    mutationFn: ({
+      storyId,
+      itemId,
+      data,
+    }: {
+      storyId: string;
+      itemId: string;
+      data: StoryItemSplit;
+    }) => apiClient.splitStoryItem(storyId, itemId, data),
     onSuccess: (_, variables) => {
       queryClient.invalidateQueries({ queryKey: ['stories'] });
       queryClient.invalidateQueries({ queryKey: ['stories', variables.storyId] });
@@ -157,6 +187,26 @@ export function useDuplicateStoryItem() {
   });
 }
 
+export function useSetStoryItemVersion() {
+  const queryClient = useQueryClient();
+
+  return useMutation({
+    mutationFn: ({
+      storyId,
+      itemId,
+      data,
+    }: {
+      storyId: string;
+      itemId: string;
+      data: StoryItemVersionUpdate;
+    }) => apiClient.setStoryItemVersion(storyId, itemId, data),
+    onSuccess: (_, variables) => {
+      queryClient.invalidateQueries({ queryKey: ['stories'] });
+      queryClient.invalidateQueries({ queryKey: ['stories', variables.storyId] });
+    },
+  });
+}
+
 export function useExportStoryAudio() {
   const platform = usePlatform();
 
@@ -165,7 +215,10 @@ export function useExportStoryAudio() {
       const blob = await apiClient.exportStoryAudio(storyId);
 
       // Create safe filename
-      const safeName = storyName.substring(0, 50).replace(/[^a-z0-9]/gi, '-').toLowerCase();
+      const safeName = storyName
+        .substring(0, 50)
+        .replace(/[^a-z0-9]/gi, '-')
+        .toLowerCase();
       const filename = `${safeName || 'story'}.wav`;
 
       await platform.filesystem.saveFile(filename, blob, [

app/src/lib/hooks/useStoryPlayback.ts

@@ -70,6 +70,16 @@ export function useStoryPlayback(items: StoryItemDetail[] | undefined) {
     }
   }, []);
 
+  // Resolve the audio buffer key and URL for an item.
+  // When a version_id is pinned, use that version's audio; otherwise use the generation default.
+  const getAudioKey = (item: StoryItemDetail) =>
+    item.version_id ? `v:${item.version_id}` : item.generation_id;
+
+  const getAudioUrlForItem = (item: StoryItemDetail) =>
+    item.version_id
+      ? apiClient.getVersionAudioUrl(item.version_id)
+      : apiClient.getAudioUrl(item.generation_id);
+
   // Preload audio files as AudioBuffers
   useEffect(() => {
     if (!items || items.length === 0) {
@@ -78,12 +88,12 @@ export function useStoryPlayback(items: StoryItemDetail[] | undefined) {
       return;
     }
 
-    const currentIds = new Set(items.map((item) => item.generation_id));
+    const currentKeys = new Set(items.map(getAudioKey));
     const audioContext = getAudioContext();
 
     // Remove buffers for items that no longer exist
     for (const [id] of audioBuffersRef.current) {
-      if (!currentIds.has(id)) {
+      if (!currentKeys.has(id)) {
         audioBuffersRef.current.delete(id);
       }
     }
@@ -91,24 +101,25 @@ export function useStoryPlayback(items: StoryItemDetail[] | undefined) {
     // Preload audio for new items
     const preloadPromises: Promise<void>[] = [];
     for (const item of items) {
-      if (!audioBuffersRef.current.has(item.generation_id)) {
-        const audioUrl = apiClient.getAudioUrl(item.generation_id);
-        console.log('[StoryPlayback] Preloading audio buffer:', item.generation_id);
+      const key = getAudioKey(item);
+      if (!audioBuffersRef.current.has(key)) {
+        const audioUrl = getAudioUrlForItem(item);
+        console.log('[StoryPlayback] Preloading audio buffer:', key);
 
         const preloadPromise = fetch(audioUrl)
           .then((response) => response.arrayBuffer())
           .then((arrayBuffer) => audioContext.decodeAudioData(arrayBuffer))
           .then((audioBuffer) => {
-            audioBuffersRef.current.set(item.generation_id, audioBuffer);
+            audioBuffersRef.current.set(key, audioBuffer);
             console.log(
               '[StoryPlayback] Preloaded buffer:',
-              item.generation_id,
+              key,
               'duration:',
               audioBuffer.duration,
             );
           })
           .catch((err) => {
-            console.error('[StoryPlayback] Failed to preload audio:', item.generation_id, err);
+            console.error('[StoryPlayback] Failed to preload audio:', key, err);
           });
 
         preloadPromises.push(preloadPromise);
@@ -216,15 +227,16 @@ export function useStoryPlayback(items: StoryItemDetail[] | undefined) {
       // Schedule new sources for items that should be playing
       for (const item of shouldBePlaying) {
         if (!activeSourcesRef.current.has(item.id)) {
-          const buffer = audioBuffersRef.current.get(item.generation_id);
+          const bufferKey = getAudioKey(item);
+          const buffer = audioBuffersRef.current.get(bufferKey);
           if (!buffer) {
-            console.warn('[StoryPlayback] Buffer not loaded for:', item.generation_id);
+            console.warn('[StoryPlayback] Buffer not loaded for:', bufferKey);
             continue;
           }
 
           // Calculate when this item should start in AudioContext time
           const itemStartContextTime = storyTimeToContextTime(item.start_time_ms);
-          
+
           // Calculate effective duration and trim offsets
           const trimStartSec = (item.trim_start_ms || 0) / 1000;
           const trimEndSec = (item.trim_end_ms || 0) / 1000;