Behaviour-neutral review cleanups for the stack:
- fuzzy_match: _preserve_unicode_in_replacement now requires the plan
(it is always precomputed by the caller), so the unused old_string param
and the plan-less fallback go away. _apply_replacements takes the
precomputed unicode_plan instead of a preserve_unicode flag, keeping the
strategy decision in fuzzy_find_and_replace where it is made.
- file_operations: _json_nonstandard_constant skips the full json.loads
when the text cannot contain NaN/Infinity (every JSON write pays this
scan), strips the BOM via the shared _strip_bom helper, and catches only
the errors json.loads can raise on str input instead of a blanket
Exception.
- backup: the --keep validator comment now states why it exists (a
negative keep slices away the newest archives).
5d579c5144