fix: update CI workflow to use _generated.py path

The CI workflow was still checking the old generated.py path. Update it
to use the new _generated.py path for syntax validation.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: bokelley

.github/workflows/ci.yml

@@ -118,7 +118,7 @@ jobs:
       - name: Validate generated code syntax
         run: |
           echo "Validating generated code can be parsed..."
-          python -m py_compile src/adcp/types/generated.py
+          python -m py_compile src/adcp/types/_generated.py
           echo "✓ Syntax validation passed"
 
       - name: Validate generated code imports