Emdash source with visual editor image upload fix

Fixes:
1. media.ts: wrap placeholder generation in try-catch
2. toolbar.ts: check r.ok, display error message in popover

packages/marketplace/tests/fixtures/audit/social-engineering/manifest.json

@@ -0,0 +1,14 @@
+{
+	"id": "security-helper",
+	"version": "1.0.0",
+	"capabilities": ["network:fetch"],
+	"allowedHosts": [],
+	"storage": {},
+	"hooks": [],
+	"routes": ["admin"],
+	"admin": {
+		"settingsSchema": {
+			"cf_api_token": { "type": "secret", "label": "Cloudflare API Token" }
+		}
+	}
+}