Promote AgentCompany-New to the repository root and retire the old app

The legacy application - its src, tests, landing site, promo assets, docs,
release tooling, CI workflows, and root configs - leaves the tree; it stays
reachable in history. Everything under AgentCompany-New moves up unchanged:
same package name, so the production userData/database path is untouched,
and e2e/build scripts already resolved paths relative to the project. The
developer cred.txt stays gitignored at its new location. Full verify:ci
passes from the new root.

src/main/app/external-url.ts

@@ -0,0 +1,6 @@
+export function normalizeExternalBrowserUrl(value: string): string {
+  const url = new URL(value);
+  if (url.protocol !== "https:") throw new Error("External URLs must use HTTPS.");
+  if (url.username || url.password) throw new Error("External URLs must not include credentials.");
+  return url.toString();
+}