run writes each member's pipeline at once under the run's random id and its named branch and says
run-started; the candidate run-<id>'s catalog-revision, handed to the runner by meshcatalogclient's
candidates hook, is read whole through the revision verb and places each member's steps and a pipeline
of each entry the members change, saying pipeline-started once each.
Builds: design 47 G §64, §373, §420, A-160, A-180, A-185, A-193, A-199
Claude-Session: https://claude.ai/code/session_01NcbgfGKaxw984XyAPfLm4h
jschoubben
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