✅ test(scripts): quiet git init warnings

tests/scripts/test_sync_standards.bats

@@ -8,7 +8,7 @@ setup() {
     export PLAYBOOK_ROOT="$(cd "$BATS_TEST_DIRNAME/../.." && pwd)"
     # 初始化测试项目
     cd "$TEST_DIR"
-    git init
+    git init -b main
     git config user.name "Test User"
     git config user.email "test@example.com"
 

tests/scripts/test_vendor_playbook.bats

@@ -11,7 +11,7 @@ setup() {
     # 创建目标项目目录
     export TARGET_DIR="$(mktemp -d)"
     cd "$TARGET_DIR"
-    git init
+    git init -b main
     git config user.name "Test User"
     git config user.email "test@example.com"
 }