fix(email-renderer): validate brand settings and apply them to AMP

packages/email-renderer/src/brand.ts

@@ -0,0 +1,42 @@
+import { string, type ValueSchema } from "@wrnexus/blocks";
+
+// Brand fields are semantic values, never arbitrary CSS declarations.
+export function brandValue(
+  defaultValue: string,
+  accepts: (value: string) => boolean,
+): ValueSchema<string> {
+  const base = string({ default: defaultValue, max: 160 });
+  return {
+    ...base,
+    parse(value, path = "value") {
+      const result = base.parse(value, path);
+      if (!result.ok) return result;
+      return accepts(result.value)
+        ? result
+        : {
+            ok: false,
+            errors: [
+              {
+                code: "email.brand",
+                message: "Unsupported brand style value.",
+                severity: "error",
+                path,
+              },
+            ],
+          };
+    },
+  };
+}
+
+export const brandColor = (fallback: string) =>
+  brandValue(fallback, (value) =>
+    /^(#[0-9a-f]{3}|#[0-9a-f]{6}|#[0-9a-f]{8}|transparent)$/i.test(value),
+  );
+export const brandFont = brandValue(
+  "Arial, sans-serif",
+  (value) => /^[a-z0-9 ,'"-]+$/i.test(value) && /[a-z]/i.test(value),
+);
+export const brandWidth = brandValue(
+  "600",
+  (value) => /^\d{2,4}$/.test(value) && Number(value) >= 240 && Number(value) <= 1200,
+);