Swipes take a longer drag and slide the reader across (#49)

At a flat 60px, a thumb scrolling slightly on the diagonal moved on to the next item by
accident. A swipe now has to cover a quarter of the reader's width, and never less than 100px,
and the reader follows the finger while it is down, so it is plain before letting go whether it
will move on. It slides off on a swipe and the next item slides in from the other side; a short
one springs back. The CHANGELOG also gets back the [0.8.3] link a stray edit had broken.

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

web/app.css

@@ -674,7 +674,7 @@ input:focus,select:focus{outline:0;border-color:var(--accent)}
 
 /* Three panes, as the original had: feeds beside, items above, the item below. */
 #split{
-  display:grid;flex:1;min-height:0;
+  display:grid;flex:1;min-height:0;overflow:hidden;  /* the reader sliding on a swipe */
   grid-template-columns:minmax(0,1fr) 270px;
   grid-template-rows:minmax(90px,var(--listh,60%)) 7px 1fr;
   grid-template-areas:"list files" "grab grab" "detail detail";