fix(street-level): expanded photo leaves with panel-hiding modes; EXPAND on iPhone; pill when Mapillary is off

Three regressions from the slimming, found in review:

- Clean View, recording and the cockpit hid the old expanded viewer with
  CSS; native fullscreen sits above all of that, so the photo stayed over the
  globe (and in recordings). While expanded, the panel now watches the
  <body> classes of those modes and leaves full screen when one starts.
- iPhone Safari has no element fullscreen, so EXPAND had disappeared there.
  Where requestFullscreen is missing but popovers exist, EXPAND opens the
  viewer as a top-layer popover sized to the viewport (it stays in the
  panel's DOM; the popover attribute is set only while open, since a closed
  popover is hidden). Checked in Chrome: the popover fills the viewport over
  the panel's backdrop filter.
- Without the provider chips, a layer that was on with Mapillary switched off
  by a share link or tool (`0.m.0`) showed ON and drew nothing. The pill now
  reads OFF with a hint, and pressing it brings Mapillary back without
  switching the layer off.

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

docs/CURRENT-STATE.md

@@ -2963,9 +2963,13 @@ MapillaryJS loads on the first photo. Opening one frames it with a single
 camera flight through the application's deferred navigation (`begin` /
 `reassert`): it releases tracking, is refused in the cockpit, and is skipped
 if newer navigation took the camera while the photo loaded; closing the photo
-cancels it. EXPAND is the browser's Fullscreen API on the viewer element
-(hidden where the API is missing). At phone width the viewer height comes from
-the rail band so the whole photo fits.
+cancels it. EXPAND is the browser's Fullscreen API on the viewer element; on
+iPhone, which has no element fullscreen, the viewer opens as a top-layer
+popover instead (hidden where neither API exists). Clean View, recording and
+the cockpit take an expanded photo out of full screen. With the layer on but
+Mapillary switched off by a link or tool, the header pill reads OFF and turns
+Mapillary back on. At phone width the viewer height comes from the rail band
+so the whole photo fits.
 
 Browser gates: `npm run qa:street-level -- --url <server>` runs against real
 Mapillary with a token; `npm run qa:street-level:fixtures` answers every