Fix direct service execution with caller workflow context returning scheduler admission instead of its requested terminal result or typed failure (#942, #943).
External workflow completion now validates a supported canonical worker protocol before parsing commands or making changes. Protocol 1.20 completion remains inline; protocol 1.21 completion uses durable scheduling. The existing two-argument WorkflowTaskBridge::complete() contract is preserved. Hosts passing an authenticated worker version use the additive ProtocolAwareWorkflowTaskBridge::completeForProtocol() role.
Reduce unnecessary retained-wait projection writes while preserving workflow progress (#899, #941).
Upgrading from 2.14.1 requires no new schema migration. Server adoption and installed consumer qualification are tracked in the linked owning issues.