fix: remove --frozen flag from lowest-direct pytest runs

Root cause identified: The --frozen flag was causing uv to validate
against the lockfile, which has anyio 4.10.0 (from highest resolution).
When running lowest-direct tests, we install anyio 4.5.0, but uv run
with --frozen was re-resolving or using the lockfile version, causing
the ImportError for RunFinishedError (which only exists in 4.11+).

Changes:
- lowest-direct tests now use: uv run --no-sync pytest
- highest tests still use: uv run --frozen --no-sync pytest
- Improved debugging to check venv directly without triggering re-resolution
- Added comparison tests between --no-sync and --frozen --no-sync

This ensures lowest-direct tests use the packages installed by
--resolution lowest-direct without interference from the lockfile.

Github-Issue: #1325

Author: felixweinberger

.github/workflows/shared.yml

@@ -59,25 +59,24 @@ jobs:
       - name: Debug - Inspect installed anyio package
         if: matrix.dep-resolution.name == 'lowest-direct'
         run: |
-          set -x
-          echo "=== Anyio Version ==="
-          uv run python -c "from importlib.metadata import version; print(version('anyio'))"
+          echo "=== Anyio version from venv (direct check) ==="
+          .venv/bin/python -c "from importlib.metadata import version; print(version('anyio'))"
 
-          echo "=== Anyio Package Location ==="
-          ANYIO_PATH=$(uv run python -c "import anyio, os; print(os.path.dirname(anyio.__file__))")
+          echo "=== Anyio location ==="
+          ANYIO_PATH=$(.venv/bin/python -c "import anyio, os; print(os.path.dirname(anyio.__file__))")
           echo "$ANYIO_PATH"
 
           echo "=== Checking for RunFinishedError in _asyncio.py ==="
           grep -n "RunFinishedError" "$ANYIO_PATH/_backends/_asyncio.py" || echo "Not found"
 
-          echo "=== First 100 lines of _asyncio.py ==="
-          head -100 "$ANYIO_PATH/_backends/_asyncio.py"
+          echo "=== Testing with 'uv run --no-sync' (what pytest will use) ==="
+          uv run --no-sync python -c "from importlib.metadata import version; print('anyio version:', version('anyio'))"
 
-          echo "=== List anyio package contents ==="
-          ls -la "$ANYIO_PATH"
+          echo "=== Comparing with 'uv run --frozen --no-sync' (old approach) ==="
+          uv run --frozen --no-sync python -c "from importlib.metadata import version; print('anyio version:', version('anyio'))" || echo "Failed with --frozen"
 
       - name: Run pytest
-        run: uv run --frozen --no-sync pytest
+        run: uv run ${{ matrix.dep-resolution.name == 'lowest-direct' && '--no-sync' || '--frozen --no-sync' }} pytest
 
   readme-snippets:
     runs-on: ubuntu-latest