fix(studio): commit lane edits through the edited element's own selection

An explicit null selection override now aborts the write instead of falling
back to domEditSelection: a caller that resolved a selection for its own
element and found none was committing onto whichever element happened to be
selected. Ease changes and the playhead keyframe toggle resolve the edited
element's animations and selection instead of the current selection's, and
lane header rows follow the real label-column width so a narrowed column no
longer hangs its value readout over the canvas.

packages/studio/src/player/components/TimelineTrackHeader.tsx

@@ -178,6 +178,7 @@ function PropertyGroupHeaderRow({
   currentTime,
   clipPercentage,
   gutterBackground,
+  columnWidth,
   onTogglePropertyGroupKeyframe,
   onSeek,
 }: {
@@ -188,6 +189,7 @@ function PropertyGroupHeaderRow({
   currentTime: number;
   clipPercentage: number;
   gutterBackground: string;
+  columnWidth: number;
   onTogglePropertyGroupKeyframe?: TimelineEditCallbacks["onTogglePropertyGroupKeyframe"];
   onSeek?: (time: number) => void;
 }) {
@@ -201,10 +203,13 @@ function PropertyGroupHeaderRow({
     <div
       data-property-group={lane.group}
       data-timeline-lane-top={getTimelineLaneTop(laneIndex)}
-      className="absolute left-0 flex items-center gap-1 px-1.5 text-[10px] text-white/65"
+      className="absolute left-0 flex items-center gap-1 overflow-hidden px-1.5 text-[10px] text-white/65"
       style={{
         top: getTimelineLaneTop(laneIndex),
-        width: LABEL_COL_W,
+        // The header column narrows to contentOrigin whenever that is under
+        // LABEL_COL_W; a lane row pinned to LABEL_COL_W then hangs its value
+        // readout over the canvas, on top of the clips it is labelling.
+        width: columnWidth,
         height: LANE_H,
         background: gutterBackground,
       }}
@@ -339,6 +344,7 @@ export function TimelineTrackHeader({
                 currentTime={currentTime}
                 clipPercentage={clipPercentage}
                 gutterBackground={theme.gutterBackground}
+                columnWidth={showTrackLabel ? LABEL_COL_W : contentOrigin}
                 onTogglePropertyGroupKeyframe={onTogglePropertyGroupKeyframe}
                 onSeek={onSeek}
               />