Fix: TypeError in layout.tsx due to missing await on async headers() (breaks run_rl_swarm.sh)

[YKaizer]

This pull request fixes a TypeScript error in modal-login/app/layout.tsx that prevents the project from building successfully.

🔥 Problem

When executing ./run_rl_swarm.sh, the following error is thrown during the server build phase (captured in yarn.log):

./app/layout.tsx:25:15
Type error: Property 'get' does not exist on type 'Promise<ReadonlyHeaders>'.

  23 |   const initialState = cookieToInitialState(
  24 |     config,
> 25 |     headers().get("cookie") ?? undefined,
     |               ^
  26 |   );
  27 |
  28 |   return (
Next.js build worker exited with code: 1 and signal: null
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

This is caused by an attempt to access .get("cookie") on a Promise instead of the resolved headers() object. The root function (RootLayout) was not declared async, so the await was missing when calling headers().

✅ Fix

• Converted RootLayout to async
• Added await headers() before reading cookie data

✅ Result

This fix resolves the TypeScript error and allows run_rl_swarm.sh to complete the build without crashing.

Let me know if you'd like me to adjust anything. Happy to iterate!