Give every palette colour a hex value an engine without oklch can read

src/ui/stylesheet-floor.test.ts

@@ -0,0 +1,14 @@
+import assert from "node:assert/strict";
+import { readdirSync, readFileSync } from "node:fs";
+import { dirname, join } from "node:path";
+import { test } from "node:test";
+import { fileURLToPath } from "node:url";
+
+const cssDir = join(dirname(fileURLToPath(import.meta.url)), "..", "..", "public", "css");
+
+test("no stylesheet declares an oklch() colour, which an engine below Chromium 111 drops", () => {
+  // A dropped custom property leaves var(--accent) invalid: white text on no background.
+  for (const file of readdirSync(cssDir).filter((f) => f.endsWith(".css"))) {
+    assert.ok(!/oklch\(/.test(readFileSync(join(cssDir, file), "utf8")), `${file} declares oklch()`);
+  }
+});