fix: improve backup directory handling and exclusion patterns

Author: mayank1513

.changeset/brave-mugs-drive.md

@@ -1,2 +1,5 @@
 ---
+"git-json-resolver": patch
 ---
+
+Improve backup directory handling by cleaning up existing backups during initialization and using proper glob patterns for exclusion

lib/src/merger.test.ts

@@ -1,3 +1,4 @@
+/* eslint-disable @typescript-eslint/no-explicit-any */
 import { describe, it, expect, vi } from "vitest";
 import { Conflict, MergeContext, mergeObject, BuiltInStrategies, statusToString } from "./merger";
 import { DROP } from "./utils";