Guard the condition-object tokens in both presets

Assert @microbit/ui's droppedConditionTokens alongside the existing
key check, for the app preset and (when linked) the brand preset: a
flat override of a { base, _onDark } token merges wholesale and
silently drops the dark-surface flip.

Author: microbit-matt-hillsdon

src/deployment/default/panda-preset.test.ts

@@ -3,7 +3,10 @@
  *
  * SPDX-License-Identifier: MIT
  */
-import { unknownSemanticTokens } from "@microbit/ui/preset-lint";
+import {
+  droppedConditionTokens,
+  unknownSemanticTokens,
+} from "@microbit/ui/preset-lint";
 import { createRequire } from "node:module";
 import { describe, expect, it } from "vitest";
 import { appPreset } from "./panda-preset";
@@ -25,6 +28,12 @@ it("app preset overrides only semantic tokens @microbit/ui defines", () => {
   expect(unknownSemanticTokens(appPreset, { introduces })).toEqual([]);
 });
 
+// A flat override of a { base, _onDark } token merges wholesale and
+// silently drops the dark-surface flip — the same failure, one door over.
+it("app preset keeps every condition the base preset's tokens carry", () => {
+  expect(droppedConditionTokens(appPreset)).toEqual([]);
+});
+
 // The private brand preset is optional — present only when linked
 // (`npm run dev:link-theme`) or installed in a brand build, exactly as
 // panda.config.ts treats it. Checked here rather than in its own repo so
@@ -46,4 +55,8 @@ describe.skipIf(!brandPreset)("private brand preset", () => {
   it("overrides only semantic tokens @microbit/ui defines", () => {
     expect(unknownSemanticTokens(brandPreset, { introduces })).toEqual([]);
   });
+
+  it("keeps every condition the base preset's tokens carry", () => {
+    expect(droppedConditionTokens(brandPreset)).toEqual([]);
+  });
 });