add timeline header

packages/z-flutter/scripts/copy-build.mjs

@@ -1,6 +1,14 @@
-import { cpSync, readFileSync, writeFileSync } from "node:fs";
+import {
+  copyFileSync,
+  cpSync,
+  existsSync,
+  readFileSync,
+  realpathSync,
+  writeFileSync,
+} from "node:fs";
 import { resolve, dirname } from "node:path";
 import { fileURLToPath } from "node:url";
+import { execFileSync } from "node:child_process";
 
 const __dirname = dirname(fileURLToPath(import.meta.url));
 const src = resolve(__dirname, "../build/web");
@@ -9,6 +17,22 @@ const dest = resolve(__dirname, "../../../apps/web/public/flutter");
 cpSync(src, dest, { recursive: true });
 console.log(`Copied Flutter build: ${src} → ${dest}`);
 
+// Copy flutter.js.map from the Flutter SDK (not included in build output)
+const flutterBin = execFileSync("which", ["flutter"], {
+  encoding: "utf-8",
+}).trim();
+const sdkBinDir = dirname(realpathSync(flutterBin));
+const flutterJsMap = resolve(
+  sdkBinDir,
+  "cache/flutter_web_sdk/flutter_js/flutter.js.map",
+);
+if (existsSync(flutterJsMap)) {
+  copyFileSync(flutterJsMap, resolve(dest, "flutter.js.map"));
+  console.log("Copied flutter.js.map from SDK");
+} else {
+  console.warn(`flutter.js.map not found at ${flutterJsMap}`);
+}
+
 // Extract buildConfig from flutter_bootstrap.js so the React app can fetch it
 const bootstrap = readFileSync(resolve(dest, "flutter_bootstrap.js"), "utf-8");
 const match = bootstrap.match(/_flutter\.buildConfig\s*=\s*({.*?});/);