Open views naming the retired Snow style on Normal

createView threw on style 'snow', so an embed host or a
show_in_gods_eye_view call holding a view from before Snow was retired
was refused outright, camera and layers included. viewFromParams read
style=snow as the recipient's own style, while the app opened the same
link on Normal.

Both now read a retired style as Normal; truly unknown names still
throw. The retired list moves to a browser-free module shared by the
view API, the share codec and visual settings.

src/view/index.js

@@ -11,6 +11,7 @@ import {
   decodeLayerStateParams,
   encodeLayerStateParams,
 } from '../data/layerState.js';
+import { RETIRED_STYLES } from '../visualStylePolicy.js';
 
 /** Visual styles by internal name, with the name share links use. */
 export const STYLE_URL_NAMES = Object.freeze({
@@ -253,6 +254,7 @@ export function createView({
 } = {}) {
   if (!Number.isFinite(camera?.lat) || !Number.isFinite(camera?.lon))
     throw new TypeError('A view needs a camera lat and lon');
+  if (RETIRED_STYLES.includes(style)) style = 'normal';
   if (style !== null && !VIEW_STYLES.includes(style))
     throw new TypeError(`Unknown view style: ${style}`);
   if (map !== null && !VIEW_MAPS.includes(map))
@@ -369,9 +371,11 @@ export function viewFromParams(params) {
       pitch_deg: number('pitch'),
     },
     layers: state?.enabledLayerIds ?? [],
-    style: Object.hasOwn(STYLES_BY_URL_NAME, params.get('style'))
-      ? STYLES_BY_URL_NAME[params.get('style')]
-      : null,
+    style: RETIRED_STYLES.includes(params.get('style'))
+      ? 'normal'
+      : Object.hasOwn(STYLES_BY_URL_NAME, params.get('style'))
+        ? STYLES_BY_URL_NAME[params.get('style')]
+        : null,
     map: VIEW_MAPS.includes(map) ? map : null,
     follow,
     annotations: annotationsFromParams(params),

src/view/index.test.mjs

@@ -127,6 +127,14 @@ test('annotations travel in the link, keeping only what the app draws', async ()
   assert.equal(viewToParams(many).has('an'), false);
 });
 
+test('a view naming the retired Snow style opens on Normal', () => {
+  const camera = { lat: 1, lon: 2 };
+  assert.equal(createView({ camera, style: 'snow' }).style, 'normal');
+  const view = viewFromParams(new URLSearchParams('lat=1&lon=2&style=snow'));
+  assert.equal(view.style, 'normal');
+  assert.equal(viewToParams(view).get('style'), 'normal');
+});
+
 test('inherited and unknown style keys do not corrupt a restored view', () => {
   for (const style of [
     'constructor',