feat: wire detail pages to explore cache for instant hydration

Artist detail page:
- Checks exploreCache for pre-loaded artist image (from search)
- Checks libraryStore for albums by this artist (by name match)
  and shows them as discography instantly before API calls
- Skips fetchArtistImage if cache already provided one

Album detail page:
- Checks exploreCache for cached album metadata (title, artist,
  year) from search results and pre-populates the header
- API calls still run to get full data (releases, tracks)

frontend/src/components/explore-album-details/explore-album-details.ts

@@ -10,6 +10,7 @@ import type {
     MBRelease,
     MBTrack,
 } from '@go/explore/Service';
+import { exploreCache } from '../../store/explore-cache';
 import '@awesome.me/webawesome/dist/components/icon/icon.js';
 
 /* ── Constants ── */
@@ -398,6 +399,21 @@ export class ExploreAlbumDetails extends LitElement {
             `[explore-album] loading: "${this.albumName}" (${mbid})`,
         );
 
+        // Phase 0: hydrate from explore cache (instant).
+        const cached = exploreCache.getAlbum(mbid);
+        if (cached) {
+            this.releaseGroup = {
+                mbid: cached.mbid,
+                title: cached.title,
+                artistCredit: cached.artistName,
+                firstReleaseDate: cached.year || '',
+                primaryType: 'Album',
+            } as MBReleaseGroup;
+            this.loadingInfo = false;
+            console.log(`[explore-album] hydrated from cache: "${cached.title}"`);
+        }
+
+        // Phase 1: API calls for full data.
         const [infoResult, releasesResult] = await Promise.allSettled([
             this.fetchReleaseGroup(mbid),
             this.fetchReleases(mbid),

frontend/src/components/explore-artist-details/explore-artist-details.ts

@@ -17,6 +17,8 @@ import type {
     LBTopReleaseGroup,
     LBSimilarArtist,
 } from '@go/explore/Service';
+import { exploreCache } from '../../store/explore-cache';
+import { libraryStore } from '../../store/library-store';
 import '@awesome.me/webawesome/dist/components/icon/icon.js';
 
 /* ── Constants ── */
@@ -646,7 +648,10 @@ export class ExploreArtistDetails extends LitElement {
             `[explore-artist] loading: "${this.artistName}" (${mbid})`,
         );
 
-        // Fire all requests in parallel — each section is independent.
+        // Phase 0: hydrate from caches (instant, no Go calls).
+        this.hydrateFromCache(mbid);
+
+        // Phase 1: fire all API requests in parallel.
         const [artistResult, tracksResult, topReleasesResult, releasesResult, similarResult] =
             await Promise.allSettled([
                 this.fetchArtist(mbid),
@@ -657,7 +662,9 @@ export class ExploreArtistDetails extends LitElement {
             ]);
 
         // Artist image is fire-and-forget — doesn't block the page.
-        this.fetchArtistImage(mbid);
+        if (!this.artistImageURL) {
+            this.fetchArtistImage(mbid);
+        }
 
         // Check which release groups are in the local library.
         this.checkLibrary();
@@ -674,6 +681,47 @@ export class ExploreArtistDetails extends LitElement {
         );
     }
 
+    /**
+     * Hydrate state from the explore cache and library store.
+     * Shows cached data instantly before API calls complete.
+     */
+    private hydrateFromCache(mbid: string) {
+        // Artist image from explore cache (populated by search results).
+        const cachedArtist = exploreCache.getArtist(mbid);
+        if (cachedArtist) {
+            if (cachedArtist.imageURL) {
+                this.artistImageURL = cachedArtist.imageURL;
+            } else if (cachedArtist.imageMedium) {
+                this.artistImageURL = cachedArtist.imageMedium;
+            } else if (cachedArtist.imageSmall) {
+                this.artistImageURL = cachedArtist.imageSmall;
+            }
+        }
+
+        // Library albums by this artist — show as discography instantly.
+        const cachedAlbums = libraryStore.cachedAlbums;
+        if (cachedAlbums) {
+            const artistName = this.artistName.toLowerCase();
+            const libraryAlbums: MBReleaseGroup[] = [];
+            for (const a of cachedAlbums) {
+                if (a.ArtistName.toLowerCase() === artistName) {
+                    libraryAlbums.push({
+                        mbid: a.MBID || '',
+                        title: a.Name,
+                        primaryType: 'Album',
+                        artistCredit: a.ArtistName,
+                        firstReleaseDate: a.Year ? String(a.Year) : '',
+                    } as MBReleaseGroup);
+                }
+            }
+
+            if (libraryAlbums.length > 0) {
+                this.releaseGroups = libraryAlbums;
+                this.loadingReleases = false;
+            }
+        }
+    }
+
     private async fetchArtist(mbid: string) {
         try {
             this.artist = await LookupArtist(mbid);