refactor(help): improve help extraction for scripts

- Standardize help section delimiters across scripts
- Update `show_help` functions to extract help text dynamically
- Enhance maintainability and readability of help-related code

scripts/install-git-cliff.sh

@@ -1,4 +1,5 @@
 #!/usr/bin/env bash
+#=== HELP START ===
 # install-git-cliff.sh – Installs the git-cliff binary
 
 # Usage:
@@ -22,6 +23,7 @@
 #   aarch64-linux-gnu / musl / apple-darwin / pc-windows-msvc
 #   i686-linux-gnu / musl / pc-windows-msvc
 #   x86_64-linux-gnu / musl / apple-darwin / pc-windows-*
+#=== HELP END ===
 set -euo pipefail
 
 REPO="orhun/git-cliff"
@@ -39,7 +41,14 @@ USER_VERSION_SPECIFIED=false
 # ───────────────────────────────────────────────
 
 # 0 Help function
-show_help() { sed -n '2,24p' "$0"; }
+show_help() {
+  sed -n '/^#=== HELP START ===/,/^#=== HELP END ===/ {
+    /^#=== HELP START ===/d
+    /^#=== HELP END ===/d
+    s/^#//
+    p
+  }' "$0"
+}
 
 # 1 Parse options (keeps old single-arg form)
 POSITIONAL=()