feat: improve template workflow and README handling

[jpke]

Summary

This PR improves the template workflow and README handling to better support the intended use case of this repository as a GitHub template.

Changes Made

1. Clarified Usage Patterns

• Updated README to prioritize GitHub template usage over cloning
• Distinguished between "set up template" vs "initialize repo" workflows
• Added clear notes about when git initialization is needed

2. Improved Template Workflow

• Move original README to docs/how_to_use_this_template.md (better naming)
• Abstract README template to .cursor/templates/project_readme.md
• Minimize workflow rules by extracting template content
• Better organization and maintainability

3. Benefits

• ✅ Cleaner, more focused workflow rules
• ✅ Template content separated from workflow logic
• ✅ Easier maintenance and updates
• ✅ Better user experience for GitHub template usage
• ✅ Preserved original documentation for reference

Files Changed

• .cursor/rules/workflow.mdc - Streamlined workflow rules
• README.md - Updated quick start and usage instructions
• .cursor/templates/project_readme.md - New template file for project READMEs

Testing

• Pre-commit hooks pass
• Template structure is logical and maintainable
• Documentation is clear and accurate