Fix a MySQL repeatable-read race where the last successful activity in a parallel group could leave its workflow waiting. The activity barrier now reads current history while holding the parent-run lock, including named storage and nested groups. Duplicate completion still wakes once. Fixes #1052.
This patch changes no schema, payload, public API or platform support. It prevents new missed continuations; it does not automatically resume runs already waiting without a continuation. Rolling back restores the defect.
Qualified with independent-connection MySQL predecessor/candidate controls and the normal database, unit, static-analysis and coverage suites. Published-package verification and all twelve supported upgrade cells passed.