refactor: Convert YAML anchor merges to one-liner syntax

Convert all 71 $parameters anchor merges from two-liner to one-liner format:
- Before: $parameters:\n        <<: *parameters-definition
- After: $parameters: { <<: *parameters-definition }

This improves readability while maintaining identical YAML semantics and
generated Python code. MyPy verification confirms no behavioral changes.

Co-Authored-By: AJ Steers <[email protected]>

Author: devin-ai-integration[bot]