Sublime-style Build-n versioning + About box

Build n = commit count, baked at build time into a gitignored
version.gen.ts (postinstall + all build scripts regenerate it). About
lives in the macOS app menu and as a footer row in the options popover
(the cross-platform path), showing build, commit, date and engines.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/bun/menu.ts

@@ -1,4 +1,5 @@
 import { ApplicationMenu, type ApplicationMenuItemConfig } from "electrobun/bun";
+import { BRANDING } from "../shared/branding";
 import type { SavedConnection } from "../shared/types";
 import type { ConnectionStore } from "./store/connections";
 
@@ -32,6 +33,8 @@ export async function applyApplicationMenu(store: ConnectionStore): Promise<void
 	ApplicationMenu.setApplicationMenu([
 		{
 			submenu: [
+				{ label: `About ${BRANDING.appName}`, action: "about" },
+				{ type: "separator" },
 				{ role: "hide" },
 				{ role: "hideOthers" },
 				{ role: "showAll" },