Fix CI: allow uv cache without lock file

Set ignore-nothing-to-cache to true to allow CI to proceed
when uv.lock is not present in the repository.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: ChanceSiyuan

.github/workflows/test.yml

@@ -20,6 +20,7 @@ jobs:
       uses: astral-sh/setup-uv@v4
       with:
         enable-cache: true
+        ignore-nothing-to-cache: true
 
     - name: Set up Python ${{ matrix.python-version }}
       run: uv python install ${{ matrix.python-version }}