Performs exact string replacements in files.

Usage:
- You must use the Read tool at least once before editing a file
- When editing text, preserve the exact indentation (tabs/spaces) as it appears in the file
- ALWAYS prefer editing existing files over writing new files
- Only use emojis if the user explicitly requests it

Parameters:
- filePath (required): The absolute path to the file to modify
- oldString (required): The text to replace
- newString (required): The text to replace it with (must be different from oldString)
- replaceAll (optional): Replace all occurrences of oldString (default false)

Error Conditions:
- The edit will FAIL if oldString is not found in the file
- The edit will FAIL if oldString is found multiple times (unless replaceAll is true)
- Provide more context in oldString to make it unique if needed

Notes:
- Use replaceAll for renaming variables or strings across a file
