Merge upstream/main: Street View rework meets i18n

Upstream's Street View rework (second imagery provider, one source at a
time, OPEN STREET VIEW button, key-alternative guidance) rewrote exactly
the street-level regions this branch localizes.

Resolved as upstream logic + re-applied localization:

- keySetupCore: new unlock copy kept as msg() data; added
  keySetupAlternativeKeyNames() returning machine values (registry key
  names) so key-setup core stays English while presentation localizes.
- New src/ui/keyGuidance.js: localized key-guidance composer shared by
  layerPanel and streetLevelPresentation (requirement sentence plus the
  "or light X to use your Y key" alternatives tail, placeholders only).
- streetLevelPresentation: keyGuidance()/presentNearest()/presentMeta
  relocalized (t/tn + formatNumber instead of toLocaleString);
  renderModes and month-precision dates kept from upstream.
- layer-panels.html: upstream row ids, sl-meta-row and the new button
  kept, data-i18n hooks re-applied (incl. OPEN STREET VIEW fallback).
- es/ru catalogs: 13 new keys, stale unlock key replaced in place.

npm run i18n: complete for es and ru. npm test: 6345/6347; the one
failure (devFreshDotenv provenance) also fails on plain upstream/main
and on the pre-merge tip here - this machine leaks OPENAI_API_KEY into
spawned children with a replaced env, so it is environmental.

src/layers/streetLevel/uiState.js

@@ -16,6 +16,8 @@ import { msg, t } from '../../i18n/index.js';
  * @property {string} hint
  * @property {string|null} error
  * @property {string} color   The source's one colour.
+ * @property {boolean} [groundClick]
+ * @property {Array<'pano'|'since'>} [filters]
  */
 
 /**
@@ -31,7 +33,7 @@ export function summarizeCoverage(providers) {
     hint:
       providers.length === 0
         ? msg('No street-level imagery providers configured')
-        : active.find((p) => p.hint)?.hint || '',
+        : [...new Set(active.map((p) => p.hint).filter(Boolean))].join(' · '),
     error: active.find((p) => p.error)?.error || null,
     keyRequired:
       active.length > 0 && active.every((p) => p.keyRequired === true),
@@ -42,13 +44,39 @@ export function summarizeCoverage(providers) {
   };
 }
 
+/**
+ * Switched-off providers that would draw with a key already set, offered
+ * while the switched-on ones lack theirs.
+ * @param {Array<ProviderSnapshot>} providers
+ * @returns {Array<{id: string, label: string, requiresKeyId: string|null}>}
+ */
+export function keyAlternatives(providers) {
+  if (!summarizeCoverage(providers).keyRequired) return [];
+  return providers
+    .filter((p) => !p.on && p.configured === true && p.keyRequired !== true)
+    .map(({ id, label, requiresKeyId }) => ({ id, label, requiresKeyId }));
+}
+
+/**
+ * The filter controls a switched-on provider honours (both when none is on).
+ * @param {Array<ProviderSnapshot>} providers
+ */
+export function filterControls(providers) {
+  const active = providers.filter((p) => p.on);
+  const honoured = (key) =>
+    active.length === 0 ||
+    active.some((p) => (p.filters ?? ['pano', 'since']).includes(key));
+  return { pano: honoured('pano'), since: honoured('since') };
+}
+
 /**
  * The panel snapshot from core state and provider snapshots. The legend has
- * one swatch per active source, then the shared selection colour.
+ * one swatch per active source that draws coverage lines, then Selected.
  * @param {{enabled: boolean, filter: object, providers: Array<ProviderSnapshot>, street: object, sequence: object}} input
  */
 export function composeUIState({
   enabled,
+  groundClickReady = false,
   filter,
   providers,
   street,
@@ -58,22 +86,23 @@ export function composeUIState({
   const active = providers.filter((p) => p.on);
   const { keyRequired, keyRejected, ...coverage } =
     summarizeCoverage(providers);
-  const legend = active.map((provider) => ({
-    key: provider.id,
-    label: provider.name,
-    color: provider.color,
-  }));
-  if (active.length)
-    legend.push({
-      key: 'selected',
-      label: t('Selected'),
-      color: COLORS.selected,
-    });
+  const legend = active
+    .filter((provider) => provider.groundClick !== true)
+    .map((provider) => ({
+      key: provider.id,
+      label: provider.name,
+      color: provider.color,
+    }));
+  if (legend.length)
+    legend.push({ key: 'selected', label: t('Selected'), color: COLORS.selected });
   return {
     enabled,
+    groundClickReady: groundClickReady === true,
     keyRequired,
+    keyAlternatives: keyAlternatives(providers),
     keyRejected,
     filter: { ...filter },
+    filterControls: filterControls(providers),
     providers: providers.map((p) => ({ ...p })),
     coverage,
     legend,