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.

app/api/game/[id]/route.test.ts

@@ -0,0 +1,53 @@
+import { afterEach, describe, expect, it, vi } from "vitest";
+import { GET } from "@/app/api/game/[id]/route";
+
+afterEach(() => {
+    vi.unstubAllGlobals();
+    vi.restoreAllMocks();
+});
+
+function contextWith(id: string) {
+    return { params: Promise.resolve({ id }) };
+}
+
+function requestWith(url: string) {
+    return new Request(url);
+}
+
+describe("GET /api/game/[id]", () => {
+    it("returns 400 for non-numeric ids", async () => {
+        const response = await GET(
+            requestWith("https://fristy.net/api/game/abc"),
+            contextWith("abc"),
+        );
+        expect(response.status).toBe(400);
+        expect(response.headers.get("Access-Control-Allow-Origin")).toBe("https://fristy.net");
+    });
+
+    it("returns 404 when no profile resolves", async () => {
+        vi.stubGlobal(
+            "fetch",
+            vi.fn(async () => ({ ok: false, status: 404 })),
+        );
+        const response = await GET(
+            requestWith("https://fristy.net/api/game/123"),
+            contextWith("123"),
+        );
+        expect(response.status).toBe(404);
+    });
+
+    it("returns 502 when upstream networking fails", async () => {
+        vi.stubGlobal(
+            "fetch",
+            vi.fn(async () => {
+                throw new Error("down");
+            }),
+        );
+        const response = await GET(
+            requestWith("https://fristy.net/api/game/123"),
+            contextWith("123"),
+        );
+        expect(response.status).toBe(502);
+        expect(response.headers.get("Access-Control-Allow-Origin")).toBe("https://fristy.net");
+    });
+});