feat(extract): add unar as fallback for RAR extraction (#13472)

Add unar as a fallback when unrar is not available for extracting
RAR files. This addresses the issue where unrar has been removed
from Homebrew due to licensing issues.

The extraction now:
- Prefers unrar if available (backward compatible)
- Falls back to unar if unrar is not found
- Shows helpful error message if neither tool is installed

plugins/extract/extract.plugin.zsh

@@ -77,7 +77,15 @@ EOF
       (*.lzma) unlzma "$full_path" ;;
       (*.z) uncompress "$full_path" ;;
       (*.zip|*.war|*.jar|*.ear|*.sublime-package|*.ipa|*.ipsw|*.xpi|*.apk|*.aar|*.whl|*.vsix|*.crx|*.pk3|*.pk4) unzip "$full_path" ;;
-      (*.rar) unrar x -ad "$full_path" ;;
+      (*.rar)
+        if (( $+commands[unrar] )); then
+          unrar x -ad "$full_path"
+        elif (( $+commands[unar] )); then
+          unar -o . "$full_path"
+        else
+          echo "extract: cannot extract RAR files: install unrar or unar" >&2
+          success=1
+        fi ;;
       (*.rpm)
         rpm2cpio "$full_path" | cpio --quiet -id ;;
       (*.7z | *.7z.[0-9]* | *.pk7) 7za x "$full_path" ;;