chore: update latest snapshot date to v6-final-before-v9-cutover

Author: github-actions[bot]

README.md

@@ -1,7 +1,7 @@
 【Cofacts 真的假的】Open Datasets
 =====
 
-Latest dataset snapshot: <!-- SNAPSHOT_DATE -->2026-03-29<!-- /SNAPSHOT_DATE -->
+Latest dataset snapshot: <!-- SNAPSHOT_DATE -->v6-final-before-v9-cutover<!-- /SNAPSHOT_DATE -->
 
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