chore: ruff auto-fixes — collapsible-else-if, if-stmt-min-max, dict.fromkeys (#23926)
PLR5501 (collapsible-else-if): 28 instances — else: if: → elif:
PLR1730 (if-stmt-min-max): 15 instances — if x<y: x=y → x=max(x,y)
C420 (dict.fromkeys): 2 instances — dictcomp → dict.fromkeys
PLR1704 (redefined-argument): 1 instance — reason → err_msg (shadow fix)
C414 (unnecessary-list): 1 instance — sorted(list(x)) → sorted(x)
28 files, -44 net lines. All mechanical, zero logic changes.
17,211 tests pass, zero regressions.
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