274-dev: correct watercourse count after the two exclusions

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S6MpcBisZYhX45oDGRRJoz

wip/274-dev.md

@@ -102,9 +102,9 @@ size OSM splits into separate ways.
 
 Cross-checked against the 国土数値情報 河川データセット (W05) via the Geoshape repository at
 国立情報学研究所 — all 561 named rivers of the 石狩川, 鵡川 and 沙流川 systems, since named
-rivers each carry their own 河川コード and are not in the 「その他」 group. 34 distinct
-names; 31 appear in both W05 and OpenStreetMap, and of those all but one agree on
-position to within 110 m.
+rivers each carry their own 河川コード and are not in the 「その他」 group. The sweep found
+34 names; two were dropped by the author (below), leaving **32**. Of those, 31 appear in
+both W05 and OpenStreetMap, and all but one agree on position to within 110 m.
 
 Offset is closest approach; under ~30 m means the road crosses it.