Bump version to 0.21.1

Author: grega

bench/results.csv

@@ -231,3 +231,11 @@ timestamp,version,machine,fixture,lines,median_ms
 2026-03-26T19:04:57Z,0.21.0,Apple_M1_Pro_8c,large_picker,439,105.8
 2026-03-26T19:04:57Z,0.21.0,Apple_M1_Pro_8c,stress,561,115.2
 2026-03-26T19:04:57Z,0.21.0,Apple_M1_Pro_8c,stress_picker,561,115.9
+2026-03-27T08:39:03Z,0.21.1,Apple_M1_Pro_8c,small,21,22.5
+2026-03-27T08:39:03Z,0.21.1,Apple_M1_Pro_8c,small_picker,21,24.0
+2026-03-27T08:39:03Z,0.21.1,Apple_M1_Pro_8c,medium,164,48.2
+2026-03-27T08:39:03Z,0.21.1,Apple_M1_Pro_8c,medium_picker,164,50.9
+2026-03-27T08:39:03Z,0.21.1,Apple_M1_Pro_8c,large,439,106.4
+2026-03-27T08:39:03Z,0.21.1,Apple_M1_Pro_8c,large_picker,439,103.7
+2026-03-27T08:39:03Z,0.21.1,Apple_M1_Pro_8c,stress,561,112.4
+2026-03-27T08:39:03Z,0.21.1,Apple_M1_Pro_8c,stress_picker,561,114.6