0.18.2: centre crosshair + locked-track selection + eye-on-lock

- Optional centre crosshair: dashed horizontal + vertical lines
  through the effective canvas centre, togglable from the HUD next
  to the crop / mask-preview / stage-preview buttons. Scales with
  zoom and stays visible inside clip-edit.
- Locked clip tracks now behave as if they weren't on the stage —
  the ci-group is listening:false + draggable:false, so selection,
  drag, and transform all pass through. deselectIfLocked also
  clears a clip-instance selection that just got locked out
  (directly or via a parent group).
- Eye toggle stays clickable on locked layer / clip-track rows —
  previous pointer-events:none rule only whitelisted the lock
  button. Hide-in-editor is orthogonal to lock.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/components/Timeline.vue

@@ -4871,7 +4871,11 @@ onBeforeUnmount(() => {
   color: var(--text-dim);
 }
 
-.track.locked .track-name .lock-btn {
+.track.locked .track-name .lock-btn,
+.track.locked .track-name .eye-btn {
+  /* Keep the eye toggle clickable on locked tracks — muting a layer
+     in the editor is orthogonal to locking it, and asking the user
+     to unlock first just to toggle visibility is annoying. */
   pointer-events: auto;
 }