Can not get responses in Popup script

Describe the bug

Hi, I am new to extension dev, I am following the examples in background forward message, but the popup can not get the message, I am bit confused what's happening here.

Based on the code, I am expecting it should receive a response and display it, but the response is actually undefined here.

I tried the suggestion here but it is still not working..
https://github.com/wxt-dev/wxt/discussions/971

Reproduction

https://github.com/wxt-dev/examples/tree/main/examples/background-message-forwarder

Steps to reproduce

run the example, see if you could get the response displayed

System Info

System:
    OS: macOS 15.2
    CPU: (10) arm64 Apple M4
    Memory: 319.52 MB / 16.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 22.12.0 - ~/.nvm/versions/node/v22.12.0/bin/node
    Yarn: 1.22.19 - /usr/local/bin/yarn
    npm: 10.9.0 - ~/.nvm/versions/node/v22.12.0/bin/npm
    pnpm: 8.6.2 - ~/Library/pnpm/pnpm
  Browsers:
    Chrome: 131.0.6778.205
    Safari: 18.2

Used Package Manager

npm

Validations

• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.

Run the examples/background-message-forwarder reproduction and inspect the popup script and background-forward-message flow described in the issue. Confirm why the popup receives undefined, then verify that the expected response is displayed when the example is run.