Show the whole nav tree without :has(), raise text contrast to 4.5:1, drop unused auth rules

src/ui/stylesheet-floor.test.ts

@@ -13,3 +13,20 @@ for (const file of readdirSync(cssDir).filter((f) => f.endsWith(".css"))) {
     assert.ok(!/oklch\(/i.test(readFileSync(join(cssDir, file), "utf8")));
   });
 }
+
+const stylesheet = readFileSync(join(cssDir, "styles.css"), "utf8").replace(/\/\*[\s\S]*?\*\//g, "");
+
+// Below Chromium 105 nothing but `:has()` reveals a folded branch, so the fold may only exist where
+// the engine can undo it.
+test("styles.css hides .nav-children only inside @supports selector(:has(a))", () => {
+  const guard = stylesheet.indexOf("@supports selector(:has(a))");
+  assert.ok(guard >= 0, "no @supports selector(:has(a)) guard");
+  const hide = /\.nav-node\s*>\s*\.nav-children\s*\{\s*display:\s*none/.exec(stylesheet);
+  assert.ok(hide && hide.index > guard, "the fold rule is missing or precedes the guard");
+  const between = stylesheet.slice(guard, hide.index);
+  assert.equal(between.split("{").length - between.split("}").length, 1, "the guard closes before the fold rule");
+});
+
+test("styles.css hides the theme switch where :has() is missing", () => {
+  assert.match(stylesheet, /@supports not selector\(:has\(a\)\)\s*\{\s*\.theme-switch\s*\{\s*display:\s*none/);
+});