chore: project scaffold, build config, scripts and README

Bun + SvelteKit (static adapter) + Electron project files, icon resources,
dev/e2e/bench scripts and the README documenting the app.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

scripts/dev-app.mjs

@@ -0,0 +1,33 @@
+// `bun run dev` runs this: Electron with --dev, restarted whenever a file in electron/ changes.
+// (Vite hot-reloads the page by itself, but the main process only loads its code once.)
+import { spawn } from 'node:child_process';
+import { watch } from 'node:fs';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+const root = path.join(path.dirname(fileURLToPath(import.meta.url)), '..');
+const electron = path.join(root, 'node_modules', '.bin', 'electron');
+let child = null;
+let restarting = false;
+let timer = null;
+
+function start() {
+  child = spawn(electron, ['.', '--dev', ...process.argv.slice(2)], { cwd: root, stdio: 'inherit' });
+  child.on('exit', (code) => {
+    if (restarting) { restarting = false; start(); return; }
+    process.exit(code ?? 0); // the window was closed: stop dev mode, as before
+  });
+}
+
+watch(path.join(root, 'electron'), { recursive: true }, (_event, file) => {
+  if (!file || !/\.(c?js|json)$/.test(file)) return;
+  clearTimeout(timer);
+  timer = setTimeout(() => {
+    console.log(`[app] ${file} changed, restarting Electron`);
+    restarting = true;
+    child.kill('SIGTERM');
+  }, 250);
+});
+
+for (const sig of ['SIGINT', 'SIGTERM']) process.on(sig, () => { restarting = false; child?.kill(sig); });
+start();