fix(config-settings): sponge bools use true/false; hint width; set -- hardening

- C1: sponge_purge_only_on_exit / sponge_allow_previously_successful are 'bool'
  rows that write true/false (sponge's convention), not on/off; badge maps
  true->ON, false->OFF, unset->DEFAULT
- I1: shorten value-page hint to 49 cols so it fits the 50-wide tier
- M1: set -U -- before the var name guards typed values beginning with a dash

functions/__config_settings_set_value.fish

@@ -38,10 +38,10 @@ function __config_settings_set_value
     else
         switch $type
             case list
-                set -U $varname (string split -n ' ' -- $value) 2>/dev/null
+                set -U -- $varname (string split -n ' ' -- $value) 2>/dev/null
             case '*'
-                # ponytail: values here are paths/ints/tokens, never leading-dash
-                set -U $varname $value 2>/dev/null
+                # -- (before the name) guards typed input that begins with a dash
+                set -U -- $varname $value 2>/dev/null
         end
     end