feat: enhance discovery, vibe sessions, and library enrichment

frontend/src/store/useVibeStore.ts

@@ -9,11 +9,14 @@ interface VibeState {
   seedTrackId: string | null;
   centerTrack: Track | null;
   buffer: Track[]; // lookahead buffer of upcoming recommended tracks
+  /** Outcome of the first V2 batch, including sessions initiated from Discover. */
+  initialBatchStatus: 'idle' | 'loading' | 'exhausted' | 'failed';
 
   setActiveSession: (session: VibeSession | null) => void;
   setSeedTrackId: (seedTrackId: string | null) => void;
   setCenterTrack: (track: Track | null) => void;
   setBuffer: (buffer: Track[]) => void;
+  setInitialBatchStatus: (status: VibeState['initialBatchStatus']) => void;
   appendBuffer: (tracks: Track[]) => void;
   shiftBuffer: () => Track | undefined;
   reset: () => void;
@@ -24,6 +27,7 @@ const initialState = {
   seedTrackId: null as string | null,
   centerTrack: null as Track | null,
   buffer: [] as Track[],
+  initialBatchStatus: 'idle' as const,
 };
 
 export const useVibeStore = create<VibeState>((set, get) => ({
@@ -39,6 +43,7 @@ export const useVibeStore = create<VibeState>((set, get) => ({
   setSeedTrackId: (seedTrackId) => set({ seedTrackId }),
   setCenterTrack: (centerTrack) => set({ centerTrack }),
   setBuffer: (buffer) => set({ buffer }),
+  setInitialBatchStatus: (initialBatchStatus) => set({ initialBatchStatus }),
   appendBuffer: (tracks) => set((state) => ({ buffer: [...state.buffer, ...tracks] })),
 
   shiftBuffer: () => {