* fix: prevent duplicate function signatures in review mode suggestions
This fixes a critical bug in the experimental review mode where GitHub
suggestions could create duplicate function signatures when applied.
The issue occurred because:
- GitHub suggestions REPLACE the entire selected line range
- Claude wasn't aware of this behavior and would include the function
signature in multi-line suggestions, causing duplication
Changes:
- Added detailed instructions about GitHub's line replacement behavior
- Provided clear examples for single-line vs multi-line suggestions
- Added explicit warnings about common mistakes (duplicate signatures)
- Improved code readability by using a codeBlock variable instead of
escaped backticks in template strings
This ensures Claude creates syntactically correct suggestions that
won't break code when applied through GitHub's suggestion feature.
* chore: format
