fix(desktop): keep identity key help dialog readable in dark mode

desktop/src/features/onboarding/ui/IdentityKeyHelpDialog.tsx

@@ -67,6 +67,7 @@ export function IdentityKeyHelpDialog() {
       <DialogContent
         className="buzz-onboarding-neutral-theme max-w-[47.5rem] -translate-y-5"
         closeButtonClassName={ONBOARDING_INK_ICON_CLASS}
+        data-system-color-scheme="light"
         data-testid="identity-key-help-dialog"
         overlayVariant="transparent"
         surface="textured"

desktop/tests/e2e/identity-key-help.spec.ts

@@ -56,3 +56,38 @@ test("identity key help explains the first-run choice", async ({ page }) => {
     "1",
   );
 });
+
+test("identity key help stays readable when the app resolves dark mode", async ({
+  page,
+}) => {
+  await page.emulateMedia({ colorScheme: "dark" });
+  await installMockBridge(page, undefined, {
+    skipCommunitySeed: true,
+    skipOnboardingSeed: true,
+  });
+  await page.goto("/");
+
+  // Fresh profiles follow the system scheme, so the emulated dark scheme is
+  // the first-run repro: the app resolves the dark theme while onboarding.
+  await expect
+    .poll(() =>
+      page.evaluate(() => document.documentElement.classList.contains("dark")),
+    )
+    .toBe(true);
+
+  const trigger = page.getByTestId("identity-key-help-trigger");
+  await expect(trigger).toHaveCSS("opacity", "1", { timeout: 5000 });
+  await trigger.click();
+
+  const dialog = page.getByTestId("identity-key-help-dialog");
+  await expect(dialog).toBeVisible();
+  await waitForAnimations(page);
+
+  // The textured powder card is baked light in both themes, so the dialog pins
+  // the neutral onboarding theme to its light variant. Without the pin the
+  // dark theme flips --foreground to near-white and the title disappears
+  // against the white card.
+  await expect(
+    dialog.getByRole("heading", { name: "What’s an identity key?" }),
+  ).toHaveCSS("color", "rgb(23, 23, 23)");
+});