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/create-window.ts

@@ -0,0 +1,43 @@
+import { BrowserWindow } from "electron";
+import { join } from "node:path";
+import { attachMainWindowSecurity } from "./window-security";
+
+export interface CreateWindowOptions {
+  preloadPath: string;
+  rendererDist: string;
+  devServerUrl?: string;
+}
+
+export function createMainWindow(options: CreateWindowOptions): BrowserWindow {
+  const win = new BrowserWindow({
+    width: 1280,
+    height: 860,
+    minWidth: 980,
+    minHeight: 700,
+    title: "AgentCompany",
+    show: false,
+    titleBarStyle: process.platform === "darwin" ? "hiddenInset" : "hidden",
+    webPreferences: {
+      preload: options.preloadPath,
+      nodeIntegration: false,
+      contextIsolation: true,
+      sandbox: true,
+      webSecurity: true,
+      allowRunningInsecureContent: false,
+    },
+  });
+
+  attachMainWindowSecurity(
+    win,
+    options.devServerUrl ? new URL(options.devServerUrl).origin : null,
+  );
+  win.once("ready-to-show", () => win.show());
+
+  if (options.devServerUrl) {
+    win.loadURL(options.devServerUrl);
+  } else {
+    win.loadFile(join(options.rendererDist, "index.html"));
+  }
+
+  return win;
+}