Why: Foundation task T0 of the UI/interaction base (proposal 2026-09-30,
D25-D33): add the new UI component library and command-bus ecosystem repos,
extend build/test/pin orchestration to twelve submodules.
Evidence: make test green on the pinned combo (core + backend 13 pkgs +
frontend 9 + ui 6 tests); make build produces bin/agent-system with combo
version string including ui; make contracts now generates to frontend and ui
with submodules staying clean; renderer/tokens migration verified
CSS-rule-identical (zero behavior change).
Impact: New modules/ui and deps/agent-command gitlinks; frontend consumes ui
via source alias; backend vendors agent-command (replace only, no import
yet); follows provider-first merges (ui PR#1/#2, agent-command PR#1,
documents PR#8, frontend PR#2, backend PR#6).
Refs: modules/documents docs/proposals/2026-09-30-ui-inbox-command-workspace.md