fix(test): handle pytest collection exit code 5 as no tests found

When pytest collects no tests, it exits with code 5 which should be treated as a valid state indicating no tests rather than an error. This change properly handles this exit code in the test workflow metadata collection step, preventing false negative workflow failures. Also moved the EAGER_IMPORT environment variable definition to the job level for better organization.

The fetch-depth comment was updated to reference Codecov's documentation instead of the previous unclear reasoning.

Author: liblaf

template/.github/workflows/test.yaml

@@ -39,7 +39,12 @@ jobs:
           if pytest --collect-only; then
             echo 'has-tests=true' >> "$GITHUB_OUTPUT"
           else
-            echo 'has-tests=false' >> "$GITHUB_OUTPUT"
+            code="$?"
+            if (("$code" == 5)); then
+              echo 'has-tests=false' >> "$GITHUB_OUTPUT"
+            else
+              exit "$code"
+            fi
           fi
 
   test:
@@ -50,11 +55,13 @@ jobs:
       - metadata
     if: needs.metadata.outputs.has-tests == 'true'
     runs-on: ubuntu-latest
+    env:
+      EAGER_IMPORT: true # ref: <https://github.com/scientific-python/lazy-loader?tab=readme-ov-file#early-failure>
     steps:
       - name: Checkout
         uses: actions/checkout@v6
         with:
-          fetch-depth: 0 # I don't know why, but it is present in the official example
+          fetch-depth: 0 # I don't know why, but it is present in Codecov's documentation
       - name: Setup Python
         uses: liblaf/actions/setup-python@v1
         with: