feat: add script catalog and -h help for all dotfile scripts

Introduce ff script -h with auto descriptions, shared help.sh, and usage flags across script/*.sh.

Co-authored-by: Cursor <cursoragent@cursor.com>

script/git-init.sh

@@ -1,11 +1,31 @@
 #!/bin/bash
+# 将 ~/.gitconfig 链接到 dotfile，并设置 Linux 凭据脚本可执行
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+# shellcheck disable=SC1091
+source "$SCRIPT_DIR/common/help.sh"
+
+usage() {
+    cat <<'EOF'
+用法: git-init
+
+备份已有 ~/.gitconfig，软链接到 ~/.dotfile/git/.gitconfig。
+同时为 git-credential-linux.sh 添加可执行权限。
+
+选项:
+  -h, --help  显示此帮助
+EOF
+}
+
+dotfile_help_requested "${1:-}" && dotfile_show_help
+
+set -euo pipefail
 
 echo 'Init git config'
 src=$HOME/.gitconfig
-if [ -f $src ]; then
-  mv $src $src.bak
+if [ -f "$src" ]; then
+    mv "$src" "$src.bak"
 fi
-ln -s $HOME/.dotfile/git/.gitconfig $src
+ln -s "$HOME/.dotfile/git/.gitconfig" "$src"
 
 chmod +x "$HOME/.dotfile/git/git-credential-linux.sh"
-