desloppify: code health overhaul plus abuse hardening (140 green, strict 87.2)

Honest baseline after removing 45 gaming suppressions. Structural: lib/game plus root hooks extraction, CORS origin echo, DEV_ORIGINS layering. Fixes: error-cause binding, discord 5xx split, null-cache guard, co-located tests, rejecting-fetch coverage, naming and typing cleanup, socket controller, cache bound, cascade helpers, latch resets. Hardening: per-IP rate limit on API routes, deterministic-miss UX, retry cooldown plus cap. Suite 140 green, build plus lint clean.

components/section-heading.test.tsx

@@ -0,0 +1,17 @@
+import { describe, expect, it } from "vitest";
+import { render, screen } from "@testing-library/react";
+import { SectionHeading } from "@/components/section-heading";
+
+describe("SectionHeading", () => {
+    it("renders kicker, title, and subtitle", () => {
+        render(<SectionHeading kicker="src" title="Title" subtitle="Sub" />);
+        expect(screen.getByText("// src")).toBeDefined();
+        expect(screen.getByRole("heading", { level: 2 }).textContent).toBe("Title");
+        expect(screen.getByText("Sub")).toBeDefined();
+    });
+
+    it("omits subtitle when absent", () => {
+        const { container } = render(<SectionHeading kicker="src" title="Title" />);
+        expect(container.querySelector("p.mt-2")).toBeNull();
+    });
+});