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.

tools/delegate_tool.py

@@ -1239,7 +1239,7 @@ def _dump_subagent_timeout_diagnostic(
         if tool_names:
             _w(f"  loaded tool count: {len(tool_names)}")
             try:
-                _w(f"  loaded tools:      {sorted(list(tool_names))}")
+                _w(f"  loaded tools:      {sorted(tool_names)}")
             except Exception:
                 pass
         _w("")