Details (original message):
Implement the three-column workbench frontend: resizable/collapsible nav with overshorthand collapse, streaming chat with part renderers and process collapse, HITL choice cards with impact display and free-input pivot, plan/todos/artifacts/agents tabs, subagent tracker modal, schema-driven settings center with effect badges and masked secrets, profile management with import/export, plugin panel rendering, doc viewer with edit-save; contract shape tests.
