feat(shell): integrate _fish_mkdir_p into mkdir and mkcd

- mkdir: loop over path args calling _fish_mkdir_p --path; falls back
  to command mkdir -p when flag args (e.g. -m 755) are present
- mkcd: default to _fish_mkdir_p --tree for new dirs; add -s/--silent
  flag to suppress tree output (mkcd's own status message still prints)

functions/_fish_mkdir_p.fish

@@ -44,12 +44,12 @@ function _fish_mkdir_p --description 'mkdir -p with configurable verbose output'
 
     if test $mode = path
         set -l display (string replace -- "$HOME" "~" $target)"/"
-        echo (set_color --bold cyan)"Created: "(set_color cyan)"$display"(set_color normal)
+        echo (set_color --bold cyan)"Created directory: "(set_color cyan)"$display"(set_color normal)
         return 0
     end
 
     # Tree mode: dimmed existing anchor, then cyan new dirs.
-    echo (set_color --bold cyan)"Created missing directories:"(set_color normal)
+    echo (set_color --bold yellow)"Created directories:"(set_color normal)
     set -l anchor (string replace -- "$HOME" "~" $cursor)"/"
     echo (set_color brblack)" $anchor"(set_color normal)
     set -l i 1