Make the world timeline a scrubber under the dock

The timeline shows whenever a layer with time to show is on, live or not.
Its track runs over the time those layers cover, reaching to now, with a
tick for each launch or frame and a handle to drag; arrows step between the
ticks, and a scrub to now goes live. The bar sits along the bottom of the
screen, and the dock and everything anchored above it rise by its height;
clean view, recording and the cockpit put it away with the dock.

src/ui/styles/status.css

@@ -390,7 +390,7 @@ html:not([lang='en']) #global-loading-detail {
 /* ── Toast Notification ──────────────────────── */
 #toast {
   position: fixed;
-  bottom: 100px;
+  bottom: calc(100px + var(--world-timeline-lift, 0px));
   left: 50%;
   transform: translateX(-50%) translateY(20px);
   z-index: 200;