fix(import): address review on metadata, bounds, navigation, clock and GPX

- Imported metadata stays inert: descriptions, native labels, properties and
  KML extended data are dropped from every entity; names are kept as short
  plain text. GeoJSON loads with a describe that builds no HTML, and
  simplestyle (including marker-symbol) is dropped, so no icon asset is
  fetched for a file and GeoJSON draws in its row's color.
- Bound geometry before loading: features and vertices are counted in the
  parsed GeoJSON, the KML document and while reading GPX, and a file over
  20,000 features or 250,000 vertices is refused before Cesium builds it.
- Imports run one batch at a time, so concurrent picks or drops cannot pass
  the 12-file cap.
- Fly-to framing walks long tracks by index instead of spreading them into a
  call.
- Fly-to is an immediate navigation through the application shell; the fly
  after an import is a deferred navigation stamped when the batch starts and
  re-asserted just before flying.
- Dated imports never change the shared clock: imported sources expose no
  clock, entities are available for all time, and a KML gx:Track is drawn as
  its line.
- GPX is read into GeoJSON with one line per track segment, without times.
- KML/KMZ rows show a hatched swatch (they keep their own styles); keyboard
  focus is kept on the same control after hide/show and moves to the next
  row after remove.
- Unit regressions for each, and the rendered QA now imports hostile
  metadata, dated KML/GPX and a two-segment track, and fails on any request
  for a file's contents or icon assets, a clock change, or surviving
  metadata.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/ui/styles/controls.css

@@ -1031,6 +1031,16 @@ body.gev-drawing #cesiumContainer canvas {
   height: 8px;
   border-radius: 2px;
 }
+/* KML/KMZ draw with the styles written in the file, so the swatch shows a
+   hatch instead of a color the globe does not use. */
+.geo-import-swatch.own-styles {
+  background: repeating-linear-gradient(
+    45deg,
+    var(--text-dim) 0 1px,
+    transparent 1px 3px
+  );
+  box-shadow: inset 0 0 0 1px var(--text-dim);
+}
 .geo-import-name {
   flex: 1 1 auto;
   min-width: 0;