refactor(street-level): simpler panel — native fullscreen, no FOLLOW button, no provider chips

EXPAND now uses the browser's Fullscreen API on the viewer element, which
stays in the panel; the hand-built modal (re-parenting to <body>, inert
siblings, focus trap, document-level Esc/Tab, Clean View/recording/cockpit
hide rules) is gone. The button is hidden where the API is missing.

The FOLLOW button and the PROVIDERS chip row are removed. The header pill is
the only layer switch and re-enables a provider switched off elsewhere; under
KEY REQUIRED the error line says which key to add. Chip colour support in
chipGroup, dead CSS and tests pinning the removed behaviour go with them.

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

src/ui/templates/layer-panels.html

@@ -86,12 +86,11 @@
           <div id="sl-viewer-wrap" class="sl-viewer-wrap" hidden>
             <div class="sl-viewer-bar">
               <div class="sl-viewer-tools">
-                <button id="sl-viewer-expand" class="scene-btn" type="button" aria-pressed="false" title="Expand the street-level view (Esc shrinks it)"><span class="sl-btn-icon" aria-hidden="true">⤢</span><span class="sl-btn-text">EXPAND</span></button>
+                <button id="sl-viewer-expand" class="scene-btn" type="button" aria-pressed="false" title="Show the street-level view full screen (Esc shrinks it)"><span class="sl-btn-icon" aria-hidden="true">⤢</span><span class="sl-btn-text">EXPAND</span></button>
                 <div class="sl-seg" role="radiogroup" aria-label="Image fit">
                   <button type="button" class="sl-seg-btn is-active" data-sl-render="letterbox" role="radio" aria-checked="true" title="Fit: show the whole photo, with dark bars where its shape differs from the frame">FIT</button>
                   <button type="button" class="sl-seg-btn" data-sl-render="fill" role="radio" aria-checked="false" tabindex="-1" title="Fill: fill the frame edge to edge, cropping the photo">FILL</button>
                 </div>
-                <button id="sl-follow-btn" class="scene-btn" type="button" aria-pressed="false" aria-label="Camera follows view" title="Camera follows view: move the globe camera wherever the street-level view looks"><span class="sl-btn-icon" aria-hidden="true">⌖</span><span class="sl-btn-text">FOLLOW</span></button>
               </div>
               <div class="sl-viewer-tools sl-viewer-tools-right">
                 <button id="sl-viewer-close" class="sl-viewer-x" type="button" title="Close the image and deselect it on the map" aria-label="Close the street-level image">×</button>
@@ -110,13 +109,8 @@
             </div>
           </div>
           <div class="sl-settings">
-            <div class="sl-providers" role="group" aria-label="Imagery providers">
-              <span class="cctv-summary-label">PROVIDERS</span>
-              <div id="sl-provider-chips" class="sl-chips"></div>
-            </div>
             <div id="sl-error" class="sl-error" role="alert" hidden><span aria-hidden="true">⚠</span> <span id="sl-error-text"></span></div>
-            <!-- A missing key gates the filters only: the chips above stay
-                 focusable so their tooltip can say how to add the key. -->
+            <!-- A missing key gates the filters; the line above says how to add it. -->
             <fieldset id="sl-controls" class="sl-controls">
               <div class="sl-filters" role="group" aria-label="Imagery filters">
                 <span class="cctv-summary-label">IMAGERY</span>