fix: address final review findings (clip reset, codecs, paths, timeline)

Co-authored-by: Cursor <cursoragent@cursor.com>

src/lib/components/Timeline.svelte

@@ -31,7 +31,9 @@
 
   $effect(() => {
     if (session.duration > 0) {
+      timelineState.visibleStart = 0;
       timelineState.visibleEnd = session.duration;
+      timelineState.zoom = 1;
     }
   });