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/tooling/streetLevelQa.test.mjs

@@ -25,7 +25,7 @@ import { redact } from '../../scripts/qa-browserEvidence.mjs';
 globalThis.requestAnimationFrame ??= (callback) =>
   setTimeout(() => callback(Date.now()), 0);
 
-test('the harness expects exactly the providers the app registers, in chip order', () => {
+test('the harness expects exactly the providers the app registers, in order', () => {
   // Any method a provider asks its source for is a no-op: only ids matter.
   const source = new Proxy({}, { get: () => () => {} });
   const layer = createApplicationStreetLevel({