Import december-2020-12-18 from private repo (scrubbed 2026-05-27)

Targets Rec Room 2020.12.18 client.

Re-import after adding:
- DorkNet.ClientMod/dorknet-clientmod.json.template — config schema
  the launcher's manifest-driven patcher renders into UserData/.
- tools/build-patcher-zip.ps1 — produces the dorknet-clientpatch-{key}.zip
  Release asset the launcher fetches.
- .github/workflows/release.yml — auto-publishes both Release assets
  on v1-december-* tag push.

Scrubbed via maintainer-side scrub-for-public.ps1: same drop rules as
the prior import, plus build-patcher-zip.ps1 added to the tools/
allow-list so it survives the scrub.

DorkNet.Server/admin-ui/src/lib/browser.ts

@@ -0,0 +1,27 @@
+// Chromium gate. The zip importer uploads multi-hundred-megabyte
+// FormData bodies and uses File / Blob slicing patterns that are
+// effectively only stable on Chromium right now:
+//   * Firefox's xhr.upload.progress + multipart streaming has buffer
+//     issues over ~500 MB.
+//   * Safari has a long-standing bug where the FormData clone for
+//     large bodies hits a memory ceiling and aborts mid-upload.
+//
+// Easier to gate the importer than to chase per-browser workarounds.
+// Other admin pages don't have this constraint, so the warning only
+// shows on the import flow.
+
+interface NavigatorWithUaData extends Navigator {
+  userAgentData?: { brands: Array<{ brand: string; version: string }> };
+}
+
+export function isChromium(): boolean {
+  if (typeof navigator === 'undefined') return true; // SSR / tests
+  // userAgentData is currently only implemented in Chromium-based
+  // browsers — Firefox/Safari haven't shipped it. If it's present,
+  // we're on Chromium.
+  if ((navigator as NavigatorWithUaData).userAgentData) return true;
+  // Fallback UA sniff for Chromium-derived browsers that haven't
+  // exposed userAgentData yet (e.g. older Edge/Brave builds).
+  const ua = navigator.userAgent;
+  return /Chrome\/|Chromium\/|Edg\//.test(ua) && !/Firefox\/|FxiOS\//.test(ua);
+}