improve build.zig; run nu tests

src/main.zig

@@ -3,7 +3,7 @@ const nu = @import("nu.zig");
 
 pub const nu_modules = .{
     App,
-    // UI,
+    UI,
 };
 pub const main = nu.main;
 

src/nu.zig

@@ -1,12 +1,13 @@
 const std = @import("std");
 const root = @import("root");
+const hooks = @import("nu/hooks.zig");
 
 pub const Window = @import("nu/Window.zig");
 pub const Render = @import("nu/Render.zig");
 pub const ImGui = @import("nu/ImGui.zig");
 
 pub const Bus = @import("nu/Bus.zig");
-pub const Hook = @import("nu/hooks.zig").Hook;
+pub const Hook = hooks.Hook;
 
 const Config = struct {
     window: Window.Config = .{},
@@ -109,3 +110,7 @@ const Graph = struct {
         return result;
     }
 };
+
+test {
+    std.testing.refAllDecls(hooks);
+}