perf(fnmatch): reject focused bracket gate

bd-2g7oyh.390

Current-head routing on vmi1227854 showed fnmatch_bracket as possible residual: FrankenLibC p50/mean 132.118/130.951 ns vs host 95.531/102.216 ns.

Focused RCH baseline selected vmi1153651 and collapsed the gap: FrankenLibC Criterion [262.82 ns 273.55 ns 285.42 ns], p50/mean 254.445/267.271 ns; host Criterion [230.13 ns 242.91 ns 264.06 ns], p50/mean 230.232/261.935 ns.

No source edit; ordering/tie-breaking/bracket syntax/PATHNAME/PERIOD/CASEFOLD/LEADING_DIR/FP/RNG/goldens unchanged by construction. Score 0.0; close no-code and route to the next profile-backed residual.

Author: Dicklesworthstone