Home button fits all of Slovakia; add an overview map, top-right

Home now fitBounds()s a country-wide bbox instead of resetting to
CENTER/ZOOM's Bratislava point, since Home resetting into the same
city you'd already be looking at wasn't useful.

The overview map is NPS's own overview plugin (npmap5-plugins, still
on an unmerged branch), vendored and converted from its UMD dist
build to a plain ES module. Patched one MapLibre API break found while
verifying it: the plugin reads map.transform (public in the MapLibre
~2.4 it targets) to relax the inset's polar pan limit; MapLibre 6 (this
app's vendored version) no longer exposes .transform at all, so it
threw on load. Guarded to skip that cosmetic adjustment when absent
instead.

public/js/map.js

@@ -14,6 +14,8 @@ import { MeasureControl } from "/js/measure.js";
 import { LAYERS_ICON } from "/js/icons.js";
 import { notifySidePanelOpen, onlyOneSidePanelOpen } from "/js/panels.js";
 import HomeButton from "/vendor/npmap-home-button/home-button.esm.js";
+import OverviewMap from "/vendor/npmap-overview/overview.esm.js";
+import * as maplibregl from "/vendor/maplibre-gl/maplibre-gl.mjs";
 
 const CENTER = [17.1077, 48.1486];
 const ZOOM = 13;
@@ -235,14 +237,18 @@ const map = new MaplibreMap({
 // all grouped together rather than split across corners. Added in this
 // order since MapLibre stacks same-position controls in add order.
 //
-// homePosition/zoom pinned to the app's own default rather than left to the
-// button's own fallback (current center/zoom at construction) — now that
-// the URL hash can restore any view on load (see the Hash option above),
-// "current view" and "the default view" are no longer the same thing, and
-// a home button that resets to wherever you happened to load the page
-// wouldn't be a home button. This is *not* "go to my location" — that's
-// GeolocateControl, below.
-map.addControl(new HomeButton({ homePosition: CENTER, zoom: ZOOM }), "top-left");
+// bounds (rather than homePosition/zoom) so Home resets to an overview of
+// the whole country, not back to CENTER/ZOOM's initial Bratislava view —
+// now that the URL hash can restore any view on load (see the Hash option
+// above), "current view" and "the default view" are no longer the same
+// thing, and a home button that resets to wherever you happened to load
+// the page wouldn't be a home button. This is *not* "go to my location" —
+// that's GeolocateControl, below.
+const SLOVAKIA_BOUNDS = [
+  [16.83, 47.73],
+  [22.57, 49.61],
+];
+map.addControl(new HomeButton({ bounds: SLOVAKIA_BOUNDS }), "top-left");
 // showCompass: false — this map never rotates, so a bearing-reset button
 // (NavigationControl's default third button) would just be dead weight.
 map.addControl(new NavigationControl({ showCompass: false }), "top-left");
@@ -257,6 +263,21 @@ map.addControl(
   "top-left",
 );
 
+// A small inset map showing where the current view sits in context — NPS's
+// own overview plugin (docs/nps-resources.adoc's "overview" entry, still on
+// an unmerged branch upstream). It draws its own embedded MapLibre map, so
+// it needs the maplibregl module itself (not just the Map class) — style
+// '' (the default) means it clones whatever the main map's current style
+// is (`this._mainMap.style.serialize()`), so it stays in sync with the
+// Online/Offline toggle without a second style to maintain here. Built only
+// once the main map's own style has loaded, matching the plugin's own
+// example — its internal map is constructed eagerly in the constructor,
+// before that clone happens in onAdd.
+map.once("style.load", () => {
+  const OverviewMapControl = OverviewMap(maplibregl);
+  map.addControl(new OverviewMapControl({}), "top-right");
+});
+
 const sidebar = document.getElementById("sidebar");
 
 const layerToggle = new LayerToggleControl(applyStyle);