reason: Completion checklist for cross-layer work


reason: Project-level constraints and protocol source of truth


reason: Verify tool registration moved off direct Python bindings as intended


reason: Verify worker output no longer requires ui_hints


reason: Verify worker event payload shape after ui_hints removal


reason: Verify history payload no longer depends on runtime ui_hints compilation


reason: Verify frontend event/history parsing matches new payload contract


reason: Verify renderer consumes tool-schema derived UI contract


reason: Verify protocol docs match implementation after refactor


reason: Verify documented data flow no longer depends on worker ui_hints


reason: Verify SSE contract documents updated worker/tool payloads