Support CRLF detection in WSL

Files on Windows use `\r\n` as the line ending whereas POSIX systems use `\n`.

This poses a problem when editing Windows files from WSL - in the `fs_read` tool, we only send the content joined by `\n`. This causes context-mismatch issues with the model whenever it attempts to make changes, since it is not expecting line endings to contain a `\r` prefix.

Instead, we should detect what line endings to use (`\r\n` vs `\n`) when editing a file since it is possible to edit Windows based files that use `\r\n` while in WSL.