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.

playwright.imaging.config.ts

@@ -15,7 +15,14 @@ export default defineConfig({
 	workers: 1,
 	retries: 1,
 	timeout: 60000,
-	expect: { timeout: 15000 },
+	expect: {
+		timeout: 15000,
+		toHaveScreenshot: {
+			animations: "disabled",
+			caret: "hide",
+			maxDiffPixelRatio: 0.02,
+		},
+	},
 	reporter: [
 		["list"],
 		["html", { outputFolder: "playwright-report/imaging", open: "never" }],