fix: auto-populate artist sort map on album page — no Artists page visit needed

ensureArtistSortMap() fetches getArtists once per session (cached) and
populates _artistSortMap automatically. Called at start of loadAlbumDetail
when showRomaji is on, so artist sort names are always available.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/api.js

@@ -95,6 +95,7 @@ let _artistRomajiMap = null; // Map<artistId, artistRomaji> — kuromoji backend
 let _artistSortMap   = null; // Map<artistId, sortName>    — Navidrome sort tag (preferred)
 let _albumRomajiMap  = null; // Map<albumName(JP), albumRomaji> — for album cards without song ID
 let _romajiIndexFetch = null; // in-flight promise dedup
+let _artistSortFetch  = null; // in-flight dedup for ensureArtistSortMap
 
 function _buildRomajiMap(idx) {
   const m  = new Map();
@@ -122,7 +123,22 @@ export async function fetchRomajiIndex() {
   return _romajiIndexFetch;
 }
 
-export function invalidateRomajiIndex() { _romajiIndex = null; _romajiMap = null; _artistRomajiMap = null; _artistSortMap = null; _albumRomajiMap = null; }
+export function invalidateRomajiIndex() { _romajiIndex = null; _romajiMap = null; _artistRomajiMap = null; _artistSortMap = null; _albumRomajiMap = null; _artistSortFetch = null; }
+
+// Ensures _artistSortMap is populated from getArtists (cached — one network call per session).
+// Safe to call from anywhere; deduplicates concurrent calls automatically.
+export async function ensureArtistSortMap() {
+  if (_artistSortMap) return;
+  if (_artistSortFetch) return _artistSortFetch;
+  _artistSortFetch = apiCached('getArtists')
+    .then(r => {
+      const all = (r?.artists?.index || []).flatMap(i => i.artist || []);
+      cacheArtistSortNames(all);
+      _artistSortFetch = null;
+    })
+    .catch(() => { _artistSortFetch = null; });
+  return _artistSortFetch;
+}
 
 // Populate _artistSortMap from Navidrome artist objects (OpenSubsonic sortName field).
 // Called whenever getArtists or getArtist data is loaded so dispArtistById can use it.

src/views/detail.js

@@ -1,6 +1,6 @@
 import { S } from '../state.js';
 import { esc, toast } from '../utils.js';
-import { api, coverUrl, itunesSearch, itunesLookupAlbum, itunesLookupArtistSongs, itunesLookupArtistAlbums, fetchRomajiIndex, dispArtistById, dispAlbumName, cacheArtistSortNames } from '../api.js';
+import { api, coverUrl, itunesSearch, itunesLookupAlbum, itunesLookupArtistSongs, itunesLookupArtistAlbums, fetchRomajiIndex, dispArtistById, dispAlbumName, cacheArtistSortNames, ensureArtistSortMap } from '../api.js';
 import { makeCard, makeAlbumCard, makeGlobalTrackItem, makeSongItem } from '../ui/components.js';
 import { playQueue, dlSongLocal, toggleStar, parseArtists } from '../player/player.js';
 import { showCtxMenu, openDlModal } from '../ui/ui.js';
@@ -378,6 +378,7 @@ export async function loadItunesAlbumDetail(album) {
 
 // ─── ALBUM DETAIL ───
 export async function loadAlbumDetail(album) {
+  if (S.cfg.showRomaji) await ensureArtistSortMap().catch(() => {});
   document.getElementById('album-back-btn').onclick = () =>
     album._fromArtist ? navigate('artist-detail', album._fromArtist) : navigate('albums');
   document.getElementById('album-detail-name').textContent = dispAlbumName(album);