Add theme system: local themes, picker, static/dynamic mode

- blob_theme: apply local or shared themes, --dynamic recolors from
  the current wallpaper without changing it, --print saves the active
  theme's colors.toml (e.g. for a dynamic palette worth keeping)
- themes/: drop-in colors.toml files that install.sh syncs into
  Omarchy's theme dir, alongside any already-installed themes
- ThemePicker widget, walker menu, and Quick Settings tile mirroring
  the existing wallpaper picker, with color-swatch previews
- blob_wallpaper no longer forces dynamic mode on every wallpaper
  change; it only recolors if you're already in dynamic mode
- install.sh: fix a new-directory mkdir bug in backup_and_copy, and
  stop backing up wallpapers/themes (.bak dirs were showing up as
  fake entries in the picker) since both are pure git mirrors

Claude-Session: https://claude.ai/code/session_011kf23kB9NsaczSYazZsWs6

scripts/blob_wallpaper.sh

@@ -85,10 +85,19 @@ return {
 }
 EOF
 
-# Apply the Blob-Dynamic theme, but skip its own background step: it
+# Only switch the active color theme to blob-dynamic if you're already
+# in dynamic mode. The palette above and the background below are kept
+# up to date regardless, so `blob_theme --dynamic` always reflects the
+# latest wallpaper — but picking a wallpaper while on a static theme
+# should change the wallpaper, not silently pull you out of it.
+#
+# When it does apply, skip omarchy-theme-set's own background step: it
 # launches swaybg asynchronously, which races with the gif handling
 # below and can leave a static swaybg frame on top of an animated gif.
-OMARCHY_THEME_SKIP_BACKGROUND=1 omarchy-theme-set "blob-dynamic"
+CURRENT_THEME_NAME=$(cat "$HOME/.config/omarchy/current/theme.name" 2>/dev/null)
+if [ "$CURRENT_THEME_NAME" = "blob-dynamic" ]; then
+    OMARCHY_THEME_SKIP_BACKGROUND=1 omarchy-theme-set "blob-dynamic"
+fi
 
 CURRENT_BACKGROUND_LINK="$HOME/.config/omarchy/current/background"
 ln -nsf "$THEME_DIR/backgrounds/$(basename "$IMAGE_PATH")" "$CURRENT_BACKGROUND_LINK"