Describe the bug

When using vanilla-extract the generated output is missing types from .css.ts.

This is caused by this condition excluding any import ending by .css.

Workaround:
I found 2 workaround:

1. Patch the lib to remove the condition (this works because I don't have any CSS import)
2. Add .js when importing/exporting from .css.ts files (but it's easy to miss one...).

Reproduction

https://github.com/etienne-sandbox/tsdown-vanilla-extract-issue

System Info

System:
    OS: macOS 15.7.2
    CPU: (12) arm64 Apple M2 Pro
    Memory: 117.47 MB / 16.00 GB
    Shell: 4.0.8 - /opt/homebrew/bin/fish
  Binaries:
    Node: 24.9.0 - /Users/etienne/.local/state/fnm_multishells/82939_1763309296783/bin/node
    npm: 11.6.0 - /Users/etienne/.local/state/fnm_multishells/82939_1763309296783/bin/npm
    pnpm: 10.22.0 - /Users/etienne/.local/state/fnm_multishells/82939_1763309296783/bin/pnpm
    Deno: 2.5.6 - /Users/etienne/.deno/bin/deno
  Browsers:
    Brave Browser: 120.1.61.104
    Chrome: 142.0.7444.162
    Firefox: 131.0.3
    Safari: 26.1

Used Package Manager

pnpm

Validations

• Follow our Code of Conduct
• Read the Contributing Guide.
• 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, please open a GitHub Discussion instead.
• The provided reproduction is a minimal reproducible of the bug.

Contributions

• I am willing to submit a PR to fix this issue
• I am willing to submit a PR with failing tests (actually just go ahead and do it, thanks!)