fix: use git fetch <branch> + checkout -B FETCH_HEAD for reliable branch switching

install_linux.sh

@@ -18,9 +18,9 @@ fi
 DEPLOY_BRANCH="${DEPLOY_BRANCH:-main}"
 
 echo ">>> 拉取最新代码（分支: $DEPLOY_BRANCH，强制覆盖本地修改）..."
-git fetch origin
-git checkout "$DEPLOY_BRANCH"
-git reset --hard "origin/$DEPLOY_BRANCH"
+git fetch origin "$DEPLOY_BRANCH"
+git checkout -B "$DEPLOY_BRANCH" FETCH_HEAD
+echo ">>> 当前 commit: $(git rev-parse --short HEAD) $(git log -1 --format=%s)"
 
 echo ">>> 安装前端依赖并构建..."
 cd frontend