Refresh buttons turn from the press to the end of their scan; quick checks keep the count (#232, #233)

The buttons followed the feeds being checked, so they stopped between one feed and the next;
7ecbe82 held them for 600 ms over each gap. Now pressing one starts it, and scan_done stops
it only when it is the end of the scan asked for: scan_done carries `only` and `forced`, so a
scheduled scan finishing first does not stop a button whose scan is queued behind it. An
error event, a job that failed without a scan_done, stops them all.

A row's spinner stood in for its unread count from the moment its feed was checked; most
checks take milliseconds, so each count blinked as the scan went by. It now waits 300 ms.

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

web/src/feedpage.ts

@@ -159,7 +159,11 @@ function renderGroup(f,kids){
 }
 
 async function feedAction(a,f){
-  if(a==='scan'){ await api('/api/fetch',{method:'POST',body:JSON.stringify({feed:f.id,force:true})}); }
+  if(a==='scan'){
+    spinStart(f.id);
+    try{ await api('/api/fetch',{method:'POST',body:JSON.stringify({feed:f.id,force:true})}); }
+    catch(e){ spinEnd(); throw e; }
+  }
   if(a==='read'){ const r=await api(`/api/feeds/${encodeURIComponent(f.id)}/read-all`,{method:'POST'}); toast(`Marked ${r.marked} read`); await loadFeeds(true); renderFeed(); loadEntries(); }
   if(a==='rm') removeFeed(f);
   if(a==='pin'){