feat(help): standardize colored --help output across functions

Add the established c_head/c_cmd/c_flag/c_dim/c_arg color scheme to
--help (or usage-on-error) output in play-media and 13 other functions
that lacked it or used an ad hoc scheme: bkg, detach, replay, p, y,
spark, wake-lock, open-url, repo-open, dng2avif, dockup, fish-deps
(__fish_deps_help), and scrub.

Also tweak the standard itself:
- c_cmd now uses plain `set_color --bold` instead of `--bold white`,
  so the command name adapts to the terminal's foreground instead of
  forcing white text that washes out on light-background themes.
  Applied across all functions already using the pattern.
- jobrunner's reset variable renamed from c_rst to c_reset to match
  the naming used everywhere else.

functions/dockup.fish

@@ -30,13 +30,18 @@ function dockup --description 'Pull and restart docker compose containers'
 
     # Handle help flags
     if contains -- -h $argv; or contains -- --help $argv
-        echo (set_color -o yellow)"Usage:"$clr_off" dockup [DIRECTORY]"
+        set -l c_head (set_color --bold cyan)
+        set -l c_cmd (set_color --bold)
+        set -l c_flag (set_color yellow)
+        set -l c_dim (set_color brblack)
+        set -l c_reset (set_color normal)
+        echo "$c_head""Usage:$c_reset $c_cmd""dockup$c_reset $c_dim""[DIRECTORY]$c_reset"
         echo ""
-        echo (set_color -u)"Options:"$clr_off
-        echo "  -h, --help    Show this help message"
+        echo "$c_head""Options:$c_reset"
+        echo "  $c_flag-h$c_reset, $c_flag--help$c_reset    Show this help message"
         echo ""
-        echo (set_color -u)"Arguments:"$clr_off
-        echo "  DIRECTORY     Optional path to the compose project (defaults to current dir)"
+        echo "$c_head""Arguments:$c_reset"
+        echo "  $c_dim""DIRECTORY$c_reset     Optional path to the compose project (defaults to current dir)"
         return 0
     end