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.

package.json

@@ -41,6 +41,7 @@
 		"test:ui": "bash scripts/with-memory-cap.sh 8g playwright test --config playwright.ui.config.ts",
 		"test:ui:update": "bash scripts/with-memory-cap.sh 8g playwright test --config playwright.ui.config.ts --update-snapshots",
 		"test:imaging": "bash scripts/with-memory-cap.sh 8g playwright test --config playwright.imaging.config.ts",
+		"test:imaging:update": "bash scripts/with-memory-cap.sh 8g playwright test --config playwright.imaging.config.ts --update-snapshots",
 		"performance:report": "node scripts/performance-report.mjs",
 		"test:integration": "bash scripts/with-memory-cap.sh 8g vitest run --config vitest.integration.config.ts"
 	},