Fix _docs_helpers.py import error in CI

- Add try/except for relative vs absolute imports in _docs_helpers.py
- Remove silent error handling in docs workflow (fail on error)

The relative import fails when markdown-code-runner executes the code
directly via sys.path.insert. The fallback to absolute import fixes this.

.github/workflows/docs.yml

@@ -61,10 +61,11 @@ jobs:
 
       - name: Run markdown-code-runner on docs
         run: |
+          set -e
           for f in docs/*.md docs/**/*.md; do
             if [ -f "$f" ]; then
               echo "Processing $f..."
-              markdown-code-runner "$f" || echo "Warning: Failed to process $f"
+              markdown-code-runner "$f"
             fi
           done