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.
rootiest