Every play button for what is playing shows pause, and pauses it

Only the player bar's button changed; the files pane's, the row's and the
toolbar's kept showing play while it played. play() now pauses when asked to play
what is already playing, which makes each of them a toggle, and syncPlayButtons()
repaints them on play, pause and ended and whenever the list or reader is drawn.

Closes #34.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

web/src/items.ts

@@ -41,6 +41,7 @@ function renderEntries(){
     return;
   }
   for(const e of S.entries) box.appendChild(epEl(e));
+  syncPlayButtons();
   if(pane) pane.scrollTop=top;
   if(S.entries.length < S.total){
     const b=document.createElement('button');
@@ -137,7 +138,7 @@ const feedName=id=>{ const f=S.feeds.find(x=>x.id===id); return f?(f.title||f.id
 /// Replaces one row with a fresh one, leaving the rest of the list and its scroll alone.
 function swapRow(e){
   const row=$(`#eps .ep[data-guid="${CSS.escape(e.guid)}"]`);
-  if(row) row.replaceWith(epEl(e));
+  if(row){ row.replaceWith(epEl(e)); syncPlayButtons(); }
 }
 
 /// Read and unread as this page last set them, and when the server had it. A list asked for
@@ -257,6 +258,7 @@ function showDetail(e){
   $('#dback').onclick=()=>showDetail(null);
   for(const root of [box,files]) if(root) $$('button[data-a]',root).forEach(b=>
     b.onclick=()=>epAction(b.dataset.a,e,null,b.dataset.enc?Number(b.dataset.enc):null));
+  syncPlayButtons();
 }
 
 /// One enclosure: a play button when the file is here, otherwise what it is and a way to get it.