## CHANGES
- Add FileChangesMarker constant for file changes section
- Update parser to use new constant marker
- Improve error messages with dynamic marker reference
- Update tests to use new marker format
- Update system documentation with new marker syntax
This commit introduces the `fabric_code` tool and the `create_coding_feature` pattern, allowing Fabric to modify existing codebases.
## CHANGES
- add `fabric_code` tool to generate JSON representation of code projects
- add `create_coding_feature` pattern to apply AI-generated code changes
- update README with `fabric_code` installation and usage
- walk file system with maximum depth and ignore list
- scan directory and return file/dir JSON data for AI model
- provide usage instructions and examples for `fabric_code`
- add file management API to system prompt for code changes
