* Update installation and quickstart documentation for JSON-first crew projects
- Revised the installation guide to reflect the new JSON-first project structure, detailing the creation of `crew.jsonc` and `agents/*.jsonc` files.
- Updated the quickstart guide to demonstrate setting up agents and tasks using JSONC format, replacing previous YAML examples.
- Enhanced the agents and tasks documentation to clarify the transition from YAML to JSONC, including examples and explanations of the new structure.
- Added notes on the classic YAML structure for legacy projects and provided guidance on migrating to the new format.
* docs: clarify json crew quickstart guidance
* docs: address json docs review feedback
