Take a hidden shape off the globe whole, and keep every drawn shape

Answers the review of bdbbc3d7 and the IC8 pass after it.

A shape hidden from Draw's list was only set to alpha 0, so the line's
flowing stroke, which keeps its own colour, stayed painted. Now:
- the world renderer's sync() sets every entity of a hidden mark to
  show = false, and FlowMaterialProperty follows the mark's alpha;
- the screen renderer does not project a hidden callout, so it is not drawn
  and cannot push a visible label aside;
- hiding acts at once, even before a mark's first frame, and with every
  mark hidden the annotations render hold is released after one last frame;
- fly_route skips a hidden route.

Hand-drawn shapes are never merged as duplicates: every one is drawn on
purpose and unnamed until its row names it, so a second pin dropped near
the first was dropped, or replaced the first when its colour differed. A
restyle the renderer cannot draw now also syncs the renderer.

Tests cover each: renderer show/hide and flow alpha, the screen skip, the
render hold and its last frame, a show with no fade-in, hidden routes, two
nearby pins, and the restyle rollback.

src/cameraVerbs.js

@@ -1746,8 +1746,13 @@ export function flyRoute(
   const speed = ROUTE_M_S[String(args.speed || 'normal').toLowerCase()]
     ? String(args.speed || 'normal').toLowerCase()
     : 'normal';
+  // A route hidden from Draw's list is not on screen, so it is not flown.
   const routes = (annoList || []).filter(
-    (a) => a.type === 'route' && Array.isArray(a.path) && a.path.length >= 2,
+    (a) =>
+      a.type === 'route' &&
+      !a.hidden &&
+      Array.isArray(a.path) &&
+      a.path.length >= 2,
   );
   if (!routes.length) {
     return {