this.addWatchFile does not work as expected if base url is specified

[anatawa12]

Describe the bug

this.addWatchFile with absolute path / id does not actually watch file specified if base url path is specified.

When we removed the base url, it works.

Reproduction

https://github.com/anatawa12/add-watch-file-test-base-url.git

Steps to reproduce

npm install and then npm run dev, then open with your browser, and then edit test.txt.
After auto refresh we should see updated test.txt contents, but actually not.

System Info

System:
    OS: macOS 15.3.1
    CPU: (10) arm64 Apple M1 Max
    Memory: 146.77 MB / 64.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 22.6.0 - /opt/n/bin/node
    Yarn: 1.22.22 - /opt/n/bin/yarn
    npm: 10.8.2 - /opt/n/bin/npm
    pnpm: 9.15.5 - /opt/n/bin/pnpm
  Browsers:
    Chrome: 134.0.6998.166
    Edge: 134.0.3124.95
    Safari: 18.3
  npmPackages:
    vite: ^6.2.0 => 6.2.5 

-----
I generally use Firefox but envinfo doesn't provide information. My Firefox version is 136.0.2 (aarch64)

Used Package Manager

npm

Logs

No response

Validations

• Follow our Code of Conduct
• 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.
• Make sure this is a Vite issue and not a framework-specific issue. For example, if it's a Vue SFC related bug, it should likely be reported to vuejs/core instead.
• 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.