feat(mod_format): Add check-only formatting with interactive diff preview; make formatting default to dry-run and extend formatting API

ts/mod_format/interfaces.format.ts

@@ -39,7 +39,18 @@ export type IPlannedChange = {
   path: string;
   module: string;
   description: string;
-  content?: string; // For create/modify operations
+  content?: string; // New content for create/modify operations
+  originalContent?: string; // Original content for comparison
   diff?: string;
   size?: number;
 };
+
+export interface ICheckResult {
+  hasDiff: boolean;
+  diffs: Array<{
+    path: string;
+    type: 'create' | 'modify' | 'delete';
+    before?: string;
+    after?: string;
+  }>;
+}