feat: click-outside deselects a selected marker

Esc was already wired but nobody stumbles onto it. A capture-phase
pointerdown listener is installed while selectedMarkerId is set; any
click that doesn't land on a .timeline-marker (or on an open
dialog/menu) clears the selection. Listener is torn down automatically
when selection clears or the component unmounts.

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

src/components/Timeline.vue

@@ -412,6 +412,23 @@ function onOutBracketPointerUp(e: PointerEvent) {
 const selectedMarkerId = ref<string | null>(null)
 const markerDrag = ref<{ id: string; startX: number; moved: boolean } | null>(null)
 
+function onOutsideMarkerPointerDown(e: PointerEvent) {
+  const el = e.target as HTMLElement | null
+  // Leave selection alone when the click lands on the marker itself
+  // (or any menu/dialog — treat anything inside a popup as "not outside").
+  if (el?.closest('.timeline-marker')) return
+  if (el?.closest('.dialog, .kf-menu, .track-menu')) return
+  selectedMarkerId.value = null
+}
+
+watch(selectedMarkerId, (id) => {
+  if (id) {
+    document.addEventListener('pointerdown', onOutsideMarkerPointerDown, true)
+  } else {
+    document.removeEventListener('pointerdown', onOutsideMarkerPointerDown, true)
+  }
+})
+
 function markerTimeFromEvent(e: PointerEvent, markerEl: HTMLElement): number {
   const ruler = markerEl.parentElement as HTMLElement | null
   if (!ruler) return 0
@@ -1878,6 +1895,7 @@ onBeforeUnmount(() => {
   ro?.disconnect()
   ro = null
   document.removeEventListener('pointerdown', onDocumentPointerDown, true)
+  document.removeEventListener('pointerdown', onOutsideMarkerPointerDown, true)
   document.removeEventListener('keydown', onKeyDown)
   document.removeEventListener('keydown', onDocumentKeyDown)
 })