fix: disable cache for lowest-direct resolution tests

The CI was failing for lowest-direct tests due to cache corruption
where packages (specifically anyio) were installed with mixed files
from different versions. This occurred because the cache was shared
between "highest" tests (which use the lockfile) and "lowest-direct"
tests (which resolve to lowest compatible versions).

Initial attempt to use --refresh-package anyio did not resolve the
issue, indicating the cache corruption is at the wheel/file level
rather than just metadata.

This fix disables caching entirely for lowest-direct tests while
keeping it enabled for highest tests. This ensures lowest-direct
tests perform clean package resolution without cache interference,
which is the correct behavior for validating minimum dependencies.

Github-Issue: #1325

Author: felixweinberger

.github/workflows/shared.yml

@@ -39,7 +39,7 @@ jobs:
         python-version: ["3.10", "3.11", "3.12", "3.13"]
         dep-resolution:
           - name: lowest-direct
-            install-flags: "--resolution lowest-direct --refresh-package anyio"
+            install-flags: "--resolution lowest-direct"
           - name: highest
             install-flags: "--frozen"
         os: [ubuntu-latest, windows-latest]
@@ -50,7 +50,7 @@ jobs:
       - name: Install uv
         uses: astral-sh/setup-uv@v3
         with:
-          enable-cache: true
+          enable-cache: ${{ matrix.dep-resolution.name != 'lowest-direct' }}
           version: 0.9.5
 
       - name: Install the project