Twenty-odd desktop files import `@assistant-ui/core` directly, but it was
never in `dependencies` — it resolved only because react 0.15 pulled core
0.3.2 and npm hoisted it to the workspace root. react 0.14.24 wants core
^0.2.19, which nests under `react/node_modules`, so the undeclared imports
stop resolving and the build fails on `@assistant-ui/core/internal`.
Declare it so resolution doesn't depend on hoisting luck either way.