feat: autotag scoring overhaul, dump-based explore index, and lyrics search

Consolidates in-progress work across autotag, explore, and library:

- autotag: beets/Picard-informed scoring engine — ID-first matching, VA
  handling, recommendation tiers, and a merged distance/rank cascade, with
  an eval harness for regression tracking.
- explore: offline MusicBrainz dump import/incremental refresh replaces the
  legacy tier crawl; index-first local search with fuzzy matching and a
  dedicated ranker; disk-free guards for dump downloads.
- library: artist-credit extraction and matching.
- lyrics: owned-library lyric search (FTS) with LRCLIB backfill.

Also: rewrite README to be user-focused, and migrate upstream to
git.ljones.me/yonlu/yellowjacket.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/wailsjs/go/explore/Service.js

@@ -2,6 +2,10 @@
 // Cynhyrchwyd y ffeil hon yn awtomatig. PEIDIWCH Â MODIWL
 // This file is automatically generated. DO NOT EDIT
 
+export function BackfillLibraryLyrics() {
+  return window['go']['explore']['Service']['BackfillLibraryLyrics']();
+}
+
 export function BrowseReleaseGroups(arg1) {
   return window['go']['explore']['Service']['BrowseReleaseGroups'](arg1);
 }
@@ -74,6 +78,10 @@ export function GetThumbnails(arg1) {
   return window['go']['explore']['Service']['GetThumbnails'](arg1);
 }
 
+export function GetTrackLyrics(arg1) {
+  return window['go']['explore']['Service']['GetTrackLyrics'](arg1);
+}
+
 export function GetTrackThumbnail(arg1, arg2, arg3, arg4) {
   return window['go']['explore']['Service']['GetTrackThumbnail'](arg1, arg2, arg3, arg4);
 }
@@ -82,14 +90,14 @@ export function GetTrackThumbnails(arg1) {
   return window['go']['explore']['Service']['GetTrackThumbnails'](arg1);
 }
 
-export function IndexNewArtists() {
-  return window['go']['explore']['Service']['IndexNewArtists']();
-}
-
 export function InvalidateIndexDiscographies() {
   return window['go']['explore']['Service']['InvalidateIndexDiscographies']();
 }
 
+export function InvalidateLibrarySync() {
+  return window['go']['explore']['Service']['InvalidateLibrarySync']();
+}
+
 export function IsIndexReady() {
   return window['go']['explore']['Service']['IsIndexReady']();
 }
@@ -110,32 +118,40 @@ export function PopulateLocalCrossReferences() {
   return window['go']['explore']['Service']['PopulateLocalCrossReferences']();
 }
 
+export function PopulateLocalCrossReferencesIfNeeded() {
+  return window['go']['explore']['Service']['PopulateLocalCrossReferencesIfNeeded']();
+}
+
+export function PrefetchReleases(arg1) {
+  return window['go']['explore']['Service']['PrefetchReleases'](arg1);
+}
+
+export function RebuildLyricsIndex() {
+  return window['go']['explore']['Service']['RebuildLyricsIndex']();
+}
+
+export function RebuildLyricsIndexIfNeeded() {
+  return window['go']['explore']['Service']['RebuildLyricsIndexIfNeeded']();
+}
+
 export function RecordSearchClick(arg1, arg2, arg3) {
   return window['go']['explore']['Service']['RecordSearchClick'](arg1, arg2, arg3);
 }
 
+export function RefreshListenCounts() {
+  return window['go']['explore']['Service']['RefreshListenCounts']();
+}
+
 export function ResolveReleaseGroupMBIDs(arg1) {
   return window['go']['explore']['Service']['ResolveReleaseGroupMBIDs'](arg1);
 }
 
-export function Search(arg1) {
-  return window['go']['explore']['Service']['Search'](arg1);
-}
-
-export function SearchArtists(arg1) {
-  return window['go']['explore']['Service']['SearchArtists'](arg1);
-}
-
 export function SearchLocal(arg1) {
   return window['go']['explore']['Service']['SearchLocal'](arg1);
 }
 
-export function SearchRecordings(arg1) {
-  return window['go']['explore']['Service']['SearchRecordings'](arg1);
-}
-
-export function SearchReleaseGroups(arg1) {
-  return window['go']['explore']['Service']['SearchReleaseGroups'](arg1);
+export function SearchLyrics(arg1) {
+  return window['go']['explore']['Service']['SearchLyrics'](arg1);
 }
 
 export function SetContext(arg1) {