fix(a11y): WCAG AA contrast retune for the Otter Orange palette (#567)

Fixes #557. Vivid fill, ink label: brand #E07832 stays on fills while primary-foreground flips to #1A1814 (5.83:1); new theme-aware ink tokens carry orange, destructive, and success text roles; opacity-modified text purged; landing, demo, and the docs fund button retuned. Guarded by a CSS-parsing unit contrast test, rebuilt axe baselines with zero contrast entries, a new landing axe smoke, and fully regenerated darwin visual baselines.

tests/e2e-landing/a11y-contrast.spec.ts

@@ -0,0 +1,26 @@
+import AxeBuilder from "@axe-core/playwright";
+import { expect, test } from "@playwright/test";
+
+/**
+ * Color-contrast smoke for the landing site (issue #557). The landing shares
+ * the Otter palette with the app but had no axe coverage, so AA regressions
+ * shipped unnoticed. Scans the pages that exercise every palette role:
+ * hero + CTA gradient + category cards (/), tool grid chips (/tools),
+ * dark sections and comparison table (/enterprise), prose links (/faq),
+ * and the SEO card grids (/self-hosted).
+ */
+
+const PAGES = ["/", "/tools", "/enterprise", "/faq", "/self-hosted"];
+
+for (const path of PAGES) {
+  test(`landing ${path} has no color-contrast violations`, async ({ page }) => {
+    await page.goto(path);
+    await page.waitForLoadState("networkidle");
+    const results = await new AxeBuilder({ page }).withTags(["wcag2aa"]).analyze();
+    const contrast = results.violations.filter((v) => v.id === "color-contrast");
+    const offenders = contrast.flatMap((v) =>
+      v.nodes.map((n) => `${n.target.join(" ")}: ${n.failureSummary?.split("\n")[1] ?? ""}`),
+    );
+    expect(offenders, `color-contrast violations on ${path}`).toEqual([]);
+  });
+}