Files like Finder, richer mini player, in-app Back/Forward, Audio tab renamed Audiobooks

- Files: multi-select, batch move/copy/delete, rename checks, sort, filter, shortcuts, drag in (files and folders) to upload with progress and retries, drag to move, drag a file out to download
- Mini player: previous, seek bar with buffered range, time, shuffle/repeat, buffering spinner, swipe for next/previous, close
- Back/Forward bar that knows what history is possible
- Audio tab is now Audiobooks

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

tools/player-test.js

@@ -7,7 +7,7 @@ class FakeAudio{constructor(){this.paused=true;this.currentTime=0;this.duration=
  addEventListener(e,f){(this._l[e]=this._l[e]||[]).push(f)} fire(e){(this._l[e]||[]).forEach(f=>f())}
  play(){this.paused=false;this.fire('play');return Promise.resolve()} pause(){if(!this.paused){this.paused=true;this.fire('pause')}} getAttribute(){return this.src||null} load(){}}
 const toasts=[];const store={d:{},get(k,d){return this.d[k]??d},set(k,v){this.d[k]=v},del(k){delete this.d[k]}};
-const el=()=>({classList:{toggle(){},add(){}},setAttribute(){},dataset:{},style:{},querySelector:()=>null,querySelectorAll:()=>[],set innerHTML(v){},set textContent(v){}});
+const el=()=>({classList:{toggle(){},add(){}},setAttribute(){},dataset:{},style:{},querySelector:()=>el(),querySelectorAll:()=>[],set innerHTML(v){},set textContent(v){}});
 const ctx={Audio:FakeAudio,store,toast:m=>toasts.push(m),px:{art:()=>'x'},icon:()=>'',esc:s=>s,fmtDur:()=>'',$:()=>el(),document:{querySelectorAll:()=>[]},
  navigator:{onLine:true},addEventListener:(e,f)=>{listeners[e]=f},setTimeout,clearTimeout,fetch:()=>new Promise(()=>{}),URL:{createObjectURL:()=>'blob:x',revokeObjectURL(){}},
  Image:class{},MediaMetadata:class{},openSheet:()=>({}),closeSheet(){},actionSheet(){},Response,URLSearchParams,AbortController,Promise,Set,Map,Date,Math,saveStateHook:0,location:{hash:''}};