refactor: use __fish_palette in small utility functions (2/2)

25 duplicated declarations replaced by 7 calls. Completes the 33 structural
conversions: 167 declarations removed, 33 calls added, and --structural
confirms every one of the 33 diffs is declaration removals plus inserted
calls only -- no rendering text touched.

functions/y.fish is the one file in the repo with no trailing newline on
main; its original file ending is preserved rather than normalised.

functions/y.fish

@@ -25,11 +25,7 @@
 function y --description 'Yank to clipboard'
     # Check for help flag
     if contains -- -h $argv; or contains -- --help $argv
-        set -l c_head (set_color --bold cyan)
-        set -l c_cmd (set_color --bold)
-        set -l c_arg (set_color cyan)
-        set -l c_dim (set_color brblack)
-        set -l c_reset (set_color normal)
+        __fish_palette
         echo "$c_head""Usage:$c_reset $c_cmd""y$c_reset $c_arg""[TEXT]$c_reset or $c_arg""[COMMAND]$c_reset | $c_cmd""y$c_reset"
         echo ""
         echo "$c_head""Examples:$c_reset"