docs: add notes test file and PRP documentation

[Wirasm]

Summary

Create a simple NOTES.md file in the root directory that serves as a test artifact for parallel execution testing in the Dylan CLI tooling. This implementation also includes comprehensive Product Requirement Prompt (PRP) documentation for the feature.

Changes

• Added NOTES.md in project root with explanatory content about its purpose as a test file
• Created PRPs/features/completed/create-notes-test-file.md with complete PRP documentation following project standards

Implementation Details

This feature was implemented following a structured PRP approach with clear phases:

1. Foundation: Reviewed project structure and documentation conventions
2. Core Implementation: Created minimal NOTES.md file following KISS and YAGNI principles
3. Documentation: Comprehensive PRP file documenting the feature requirements and implementation plan

The NOTES.md file is intentionally minimal to serve as a lightweight test artifact for validating parallel execution capabilities without introducing unnecessary complexity.

See: PRPs/features/completed/create-notes-test-file.md for complete implementation details and acceptance criteria.

Testing

• File exists at expected location (project root)
• File contains proper markdown formatting
• File is readable and accessible
• PRP documentation follows project conventions
• No regressions in existing functionality

Related Files Modified

• New file: NOTES.md
• New file: PRPs/features/completed/create-notes-test-file.md