Wrong-target edits (the test_run_aside pass clobber, the edit_replace
mangling) were silent: the success message reported counts only, so the
model had no signal it replaced the wrong thing until later.
edit_lineno now reports the first removed line ("first: 'pass'") and
edit_replace reports the matched pattern ('old' -> 'new'), giving the
model an immediate self-correction signal.
Default still replaces first match only. Report how many matches were
found, how many replaced, and remaining hits so agents can raise
max_replaces or narrow old_string.
NCBM