[Copilot]

The test GitHub Actions job failed before pytest because uv sync --locked rejected uv.lock under a newer uv resolver. This change stabilizes CI dependency resolution so lockfile checks are deterministic across runs.

• Root cause addressed

  • The workflow implicitly installed the latest uv, allowing resolver behavior to change independently of repository commits.
  • uv sync --locked then failed on main with: “lockfile needs to be updated”.

• Workflow change

  • Updated .github/workflows/tests.yml to pin uv in astral-sh/setup-uv.
  • Preserves existing flow (uv sync --locked then uv run pytest) while removing tool-version drift as a failure mode.

• Resulting behavior

  • CI now uses a fixed uv toolchain, so lockfile enforcement is tied to repo changes, not external uv releases.

- uses: astral-sh/setup-uv@v6
  with:
    version: "0.13.7"
    enable-cache: true