test(imaging): broaden coverage across contract, transcode, routing and pixels

Environment-independent contract tests (cache headers + source, CORS, OPTIONS
preflight, negative figure/badge tables, concurrency burst) run in both the
deploy gate and the cross-browser job.

CMS-only /imaging assertions (webp/avif transcode, animated-APNG passthrough,
s-maxage edge caching) live in cms-imaging.spec.ts and are skipped behind the
edge proxy; the public topology has its own public-routing.spec.ts smoke that
fails if the edge ever stops fronting the imager or starts shadowing the CMS
endpoints. A committed per-engine visual baseline pins the static render.

The cross-browser imaging job is now blocking (IMAGING_EDGE=1), so avatar
imaging on chromium/firefox/webkit is a required signal.

e2e/imaging/public-routing.spec.ts

@@ -0,0 +1,39 @@
+import { expect, test } from "@playwright/test";
+import {
+	avatarPath,
+	IMAGER_PATH,
+	IS_EDGE,
+	looksLikeImage,
+} from "./imaging-target";
+
+// Regression guard for the public topology: the edge proxy must front the
+// imager container at `/imaging/*` while `/api/imaging/*` reaches the CMS.
+// Mis-routing here blanks avatars for every visitor, and no unit test sees it.
+// Only meaningful against the public origin, so it is skipped when the CMS is
+// reached directly (set `IMAGING_EDGE=1` for the public origin).
+test.skip(
+	!IS_EDGE,
+	"Public routing is only asserted against the edge-fronted origin",
+);
+
+test("the edge serves the imager endpoint as an image", async ({ request }) => {
+	const response = await request.get(IMAGER_PATH({ img_format: "png" }));
+	expect(response.status()).toBe(200);
+	expect(response.headers()["content-type"]).toContain("image/");
+	expect(looksLikeImage(await response.body())).toBe(true);
+});
+
+test("the CMS avatar endpoint is reachable through the edge", async ({
+	request,
+}) => {
+	const response = await request.get(avatarPath({ img_format: "png" }));
+	expect(response.status()).toBe(200);
+	expect(response.headers()["content-type"]).toContain("image/");
+	expect(looksLikeImage(await response.body())).toBe(true);
+});
+
+test("the edge does not shadow the CMS badge endpoint", async ({ request }) => {
+	const response = await request.get("/api/imaging/badge?code=ADM");
+	expect(response.status()).toBe(200);
+	expect(response.headers()["content-type"]).toContain("image/");
+});