The Edit tool falls back to a whitespace-tolerant fuzzy match when oldText does not match byte-for-byte. On a fuzzy hit it replaced text inside a whitespace-normalized copy of the whole file and wrote that copy back, so every untouched line lost its original indentation (runs of spaces/tabs collapsed to a single space). For indentation-sensitive files such as Python this silently corrupts the file.
Locate the fuzzy match in the original content with a whitespace-flexible regex and return offsets into that original content, so only the matched region is replaced. Adds regression tests.
Co-authored-by: Cursor <cursoragent@cursor.com>
