Why: Repeated progress and coupled scrolling obscured chat, and task choices lacked a reliable independent interaction path.
Evidence: 285 frontend unit tests and 23 browser scenarios pass locally before the shared event-loader extraction; final combination checks follow in Dev.
Impact: Coalesce cumulative progress, retain execution records, show timestamps and quiet notifications, support versioned work actions and explicit result references without automatic chat backfill.
Refs: feature/workbench-flow-completion
