Share pixbufs between frames panel and scrub bar — single disk read per frame

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cht/window.py

@@ -647,9 +647,9 @@ class ChtWindow(Adw.ApplicationWindow):
             self._frames_panel.load_items(items)
             self._known_frames = {item["id"] for item in items}
             self._agent_output.append(f"  Loaded {len(items)} frame thumbnails.\n")
-            # Update scrub bar thumbnails
-            self._timeline_controls.scrub_bar.set_frames(
-                [{"timestamp": e["timestamp"], "path": str(e["path"])} for e in entries]
+            # Update scrub bar thumbnails — reuse already-loaded pixbufs
+            self._timeline_controls.scrub_bar.set_frames_from_pixbufs(
+                [{"timestamp": it["timestamp"], "pixbuf": it["pixbuf"]} for it in items]
             )
 
     def _load_existing_transcript(self):
@@ -676,7 +676,7 @@ class ChtWindow(Adw.ApplicationWindow):
                 pixbuf = GdkPixbuf.Pixbuf.new_from_file_at_scale(str(entry["path"]), 256, 144, True)
                 auto = self._timeline.state.live and not self._transcript_panel.has_selection
                 self._frames_panel.add_item(fid, pixbuf, entry["timestamp"], auto_select=auto)
-                self._timeline_controls.scrub_bar.add_frame(entry["timestamp"], str(entry["path"]))
+                self._timeline_controls.scrub_bar.add_frame_from_pixbuf(entry["timestamp"], pixbuf)
             except Exception as e:
                 log.warning("Thumbnail load failed for %s: %s", fid, e)
         return True