## Summary
- keep the RDoc cheatsheet focused on RDoc markup and directives
- move YARD-specific tags into a dedicated YARD cheatsheet
- update both references against current official documentation
## Why
The existing RDoc sheet mixes RDoc directives with YARD tags such as
`@param`, `@return`, `@raise`, and `@option`. This makes the examples
look like native RDoc syntax.
The new split keeps each reference accurate and easier to scan.
Closes#2176.
Closes#2172.
## Checks
- Prettier passes for both Markdown files
- frontmatter and fenced code blocks verified
- no promotional links or unrelated changes
