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]>

docs/CURRENT-STATE.md

@@ -2938,15 +2938,16 @@ Street Level is a collapsible right-rail panel (`#street-level-panel`, layer
 token `0`, option owner `street-level`, panel `ui` token `t`) that starts
 collapsed. It opens itself only when the user, voice or a tool switches the
 layer on or a photo opens, never on a restore, and those opens are not stored.
-Like the iD editor's photo overlay, it has one chip per registered provider,
+Like the iD editor's photo overlay, it has one switch per registered provider
+(share options, no panel chips),
 shared 360°/flat and captured-since filters (relative days, so a link keeps its
 meaning), one viewer host and one on-globe credit per active provider. Each
 provider draws in one colour (`PROVIDER_COLORS` in
 `src/layers/streetLevel/policy.js`); 360° cones are rings and the selected
 sequence is GEV cyan. Share options: `m` (Mapillary), `p` (`a`/`p`/`f`
 panoramas), `s` (since, days). Only Mapillary is registered. Without
-`MAPILLARY_CLIENT_TOKEN` the panel reads KEY REQUIRED and the controls are
-disabled. With it, coverage draws as z0–5 overview points from orbit and z11–14
+`MAPILLARY_CLIENT_TOKEN` the panel reads KEY REQUIRED, its error line says
+which key to add, and the filters are disabled. With it, coverage draws as z0–5 overview points from orbit and z11–14
 sequence lines below 60 km; the proxy strips the unused `image` layer from z14
 tiles (12 MB → ~80 KB) and shares one upstream fetch between concurrent
 requests for a tile.
@@ -2968,16 +2969,16 @@ miss cooldown. Roads on elevated decks are still drawn at
 ground level. Framing a photo ignores mesh samples far below the bare earth
 (unloaded tiles).
 
-The header pill is the layer switch. With one provider its chip is a layer
-switch too; with several, darkening the last lit chip turns the layer off. The
-viewer sits under the header with EXPAND, FIT/FILL, FOLLOW and close above the
-image. FOLLOW needs the Google 3D map stack (`attachMapStackController`) and
-stops when the stack changes. Camera moves go through the application's
-navigation (`attachNavigation`), which releases aircraft and satellite tracking
-and is refused in the cockpit: turning FOLLOW on claims the camera at once, and
-FOLLOW stops when another feature takes it; a photo takes a deferred ticket
-when it starts opening and frames only if nothing newer took the camera while
-it loaded. SINCE is a stepped slider whose readout names the
+The header pill is the only layer switch; switching on also turns back on a
+provider a share link or tool switched off. The viewer sits under the header
+with EXPAND, FIT/FILL and close above the image. EXPAND is the browser's
+Fullscreen API on the viewer element, which stays in the panel (Esc or SHRINK
+leaves; the button is hidden where the API is missing). There is no FOLLOW
+button; the layer's `setFollow` has no panel control. Camera moves go through
+the application's navigation (`attachNavigation`), which releases aircraft and
+satellite tracking and is refused in the cockpit; a photo takes a deferred
+ticket when it starts opening and frames only if nothing newer took the camera
+while it loaded. SINCE is a stepped slider whose readout names the
 cut-off date. At phone width (≤720 px) the viewer height is derived from the
 rail band so the whole photo fits.
 
@@ -2988,7 +2989,7 @@ add a provider: implement the definition, register it in
 `src/app/layers/streetLevel.js`, add its boolean option to the `street-level`
 group in `src/data/layerState.js` and its modules to
 `scripts/package-boundaries.json`. Once a keyless provider registers, the
-layer's `requiresKeyId` becomes null and the key gate moves to the chips.
+layer's `requiresKeyId` becomes null and the key gate must move per provider.
 
 Street Level has two browser gates. `npm run qa:street-level -- --url <server>`
 runs against real Mapillary and needs `MAPILLARY_CLIENT_TOKEN`. `npm run