Share one theme color resolver across consumers

Five scripts each hand-rolled colors.toml parsing plus their own
alias/fallback cascade, and the tables had drifted: theme-osc grew a
divergent color8/color9 chain, tmux and gnome carried private mode
detection, and the preview tool duplicated the lot. The differences
never mattered for shipped themes but were a standing bug factory for
sparse user themes.

omarchy-theme-color is now the single resolver. Its cascade is a
verbatim port of the canonical theme-set-templates logic (semantic
keys, legacy colorN aliases, derived shades, selection/cursor
derivation, mode precedence), exposed as --all, --raw, or single-key
lookup with fallback.

Generated output is byte-identical across all 21 shipped themes on
every surface: 17 template files, OSC byte stream, tmux and gsettings
command logs, and previews. Sparse legacy themes now resolve the same
palette everywhere instead of five slightly different ones.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

bin/omarchy-theme-set-gnome

@@ -13,33 +13,9 @@ fi
 THEME_DIR=$HOME/.local/state/omarchy/current/theme
 COLORS_FILE="$THEME_DIR/colors.toml"
 
-# In-tree light themes now declare `mode = "light"` in colors.toml instead of
-# shipping a separate light.mode marker. Keep light.mode as a user-theme fallback.
-theme_mode() {
-  [[ -f $COLORS_FILE ]] || return
-
-  awk -F= '
-    {
-      field = $1
-      gsub(/^[[:space:]]+|[[:space:]]+$/, "", field)
-      if (field == "mode") {
-        value = $2
-        gsub(/^[[:space:]]+|[[:space:]]+$/, "", value)
-        if (value ~ /^"/) {
-          sub(/^"/, "", value)
-          sub(/".*$/, "", value)
-        }
-        print value
-        exit
-      }
-    }
-  ' "$COLORS_FILE"
-}
-
-mode=$(theme_mode)
-if [[ -z $mode && -f $THEME_DIR/light.mode ]]; then
-  mode="light"
-fi
+# omarchy-theme-color resolves mode from colors.toml (`mode = "light"`), a
+# legacy light.mode marker beside it, or background luminance for user themes.
+mode=$(omarchy-theme-color --file "$COLORS_FILE" mode)
 
 if [[ $mode == "light" ]]; then
   gsettings set org.gnome.desktop.interface color-scheme "prefer-light"