docs: Add inline description to $parameters in declarative component schema

- Add title and description to all $parameters fields in the schema
- Explain automatic parameter propagation mechanism
- Document that parameters are applied to component fields when not already set
- Link to comprehensive documentation page for details
- This description will appear in the Connector Builder UI and YAML Reference docs

Requested by: AJ Steers (@aaronsteers)

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

Author: devin-ai-integration[bot]