do to formatters

apps/website/lib/contracts/formatters/Formatter.ts

@@ -1,22 +1,40 @@
 /**
  * Formatter contract
- * 
+ *
  * Deterministic, reusable, UI-only formatting/mapping logic.
- * 
- * Based on DISPLAY_OBJECTS.md:
- * - Class-based
- * - Immutable
+ *
+ * Based on FORMATTERS.md:
+ * - Stateless (Formatters) or Immutable (Display Objects)
  * - Deterministic
  * - Side-effect free
- * - No Intl.* or toLocale*
  * - No business rules
+ *
+ * Uncle Bob says: "Data structures should not have behavior."
+ * Formatters ensure ViewData remains a dumb container of primitives.
  */
 
 export interface Formatter {
   /**
-   * Format or map the display object
-   * 
-   * @returns Primitive values only (strings, numbers, booleans)
+   * Format or map the input to a primitive value
+   *
+   * @returns Primitive values only (strings, numbers, booleans, null)
    */
-  format(): unknown;
+  format(): string | number | boolean | null;
+}
+
+/**
+ * Rich Display Object contract (Client-only)
+ *
+ * Used by ViewModels to provide a rich API to the UI.
+ */
+export interface DisplayObject {
+  /**
+   * Primary primitive output
+   */
+  format(): string | number | boolean | null;
+  
+  /**
+   * Multiple primitive variants
+   */
+  variants?(): Record<string, string | number | boolean | null>;
 }