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/ui/templates/layer-panels.html

@@ -118,7 +118,7 @@
             <!-- A missing key gates the filters only: the chips above stay
                  focusable so their tooltip can say how to add the key. -->
             <fieldset id="sl-controls" class="sl-controls">
-              <div class="sl-filters" role="group" aria-label="Imagery filters" data-i18n-aria-label>
+              <div id="sl-pano-row" class="sl-filters" role="group" aria-label="Imagery filters" data-i18n-aria-label>
                 <span class="cctv-summary-label" data-i18n>IMAGERY</span>
                 <div class="sl-seg" role="radiogroup" aria-label="Panorama filter" data-i18n-aria-label>
                   <button type="button" class="sl-seg-btn is-active" data-sl-pano="all" role="radio" aria-checked="true" data-i18n>ALL</button>
@@ -126,14 +126,18 @@
                   <button type="button" class="sl-seg-btn" data-sl-pano="flat" role="radio" aria-checked="false" tabindex="-1" data-i18n>FLAT</button>
                 </div>
               </div>
-              <div class="sl-since">
+              <div id="sl-since-row" class="sl-since">
                 <label class="cctv-summary-label" for="sl-since" data-i18n>SINCE</label>
                 <input id="sl-since" class="sl-range" type="range" min="0" max="8" step="1" value="0" aria-valuetext="ANY DATE" aria-describedby="sl-since-label" />
                 <output id="sl-since-label" class="sl-since-label" for="sl-since">ANY DATE</output>
               </div>
             </fieldset>
             <ul id="sl-legend" class="sl-legend" aria-label="Coverage colours" data-i18n-aria-label></ul>
-            <div id="sl-coverage-meta" class="sl-meta"></div>
+            <!-- The hint says how to open imagery; the button does it without a pointer. -->
+            <div class="sl-meta-row">
+              <div id="sl-coverage-meta" class="sl-meta"></div>
+              <button id="sl-nearest-btn" class="scene-btn sl-nearest-btn" type="button" hidden data-i18n>OPEN STREET VIEW</button>
+            </div>
           </div>
         </div>
       </div>