Test librarian with new wrkflw

.github/workflows/experiment.yaml

@@ -0,0 +1,85 @@
+name: CI
+on: [pull_request]
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
+jobs:
+  # =========================================================
+  # 1. DISCOVERY 
+  # =========================================================
+  discover:
+    runs-on: ubuntu-latest
+    outputs:
+      packages: ${{ steps.parse.outputs.packages }}
+    steps:
+      - uses: actions/checkout@v4
+      - id: changes
+        uses: tj-actions/changed-files@v44
+        with:
+          files: packages/**
+
+      # Bulletproof directory extraction (ignores file names)
+      - id: parse
+        name: Extract Package Directories
+        env:
+          ALL_FILES: ${{ steps.changes.outputs.all_changed_files }}
+        run: |
+          PKGS=$(echo "$ALL_FILES" | tr ' ' '\n' | cut -d'/' -f1,2 | sort -u | tr '\n' ' ')
+          echo "packages=$PKGS" >> $GITHUB_OUTPUT
+
+  # =========================================================
+  # 2. EXECUTION (Parallelized internally via xargs)
+  # =========================================================
+  unit:
+    needs: discover
+    if: ${{ needs.discover.outputs.packages != '' }}
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        # Exactly 5 Jobs total. Never violates GitHub limits.
+        python: ["3.9", "3.10", "3.11", "3.12", "3.14"]
+
+    name: Unit (Python ${{ matrix.python }})
+    steps:
+      - uses: actions/checkout@v4
+      - uses: astral-sh/setup-uv@v5
+        with:
+          python-version: ${{ matrix.python }}
+          enable-cache: true
+
+      - name: Run Tests Concurrently
+        run: |
+          export NOX_DEFAULT_VENV_BACKEND=uv
+          export UV_PRERELEASE=allow
+
+          # Dropped -n 1 to fix the xargs warning.
+          echo "${{ needs.discover.outputs.packages }}" | tr ' ' '\n' | xargs -P 4 -I {} sh -c '
+            if [ -f "{}/noxfile.py" ]; then
+              cd {}
+
+              # Run test and capture output
+              uvx --with "nox[uv]" nox -s "unit-${{ matrix.python }}" > nox_output.log 2>&1
+              STATUS=$?
+
+              # Print output cleanly inside a GitHub group
+              echo "::group::Testing {} (Python ${{ matrix.python }})"
+              cat nox_output.log
+
+              if [ $STATUS -ne 0 ]; then
+                # Check if it failed just because the Python version isn"t supported by this package
+                if grep -q "Sessions not found:" nox_output.log; then
+                  echo "⏭️ Session unit-${{ matrix.python }} is not defined for this package. Safely skipping."
+                else
+                  echo "❌ Tests failed in {}!"
+                  echo "::endgroup::"
+                  # Exit 1 allows other packages to finish testing, but ensures the workflow fails
+                  exit 1
+                fi
+              fi
+
+              echo "::endgroup::"
+            fi
+          '