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

themes/README.md

@@ -0,0 +1,60 @@
+# Themes
+
+Drop-in static color themes. Each subdirectory here becomes a theme
+selectable from `blob_theme`, the theme picker widget, and the walker
+menu, once `install.sh` copies it into `~/.config/omarchy/themes/`.
+
+## Adding a theme
+
+Create a directory named after the theme (lowercase, hyphens instead
+of spaces — e.g. `tokyo-night/`) containing a `colors.toml`:
+
+```toml
+accent = "#7aa2f7"
+cursor = "#c0caf5"
+foreground = "#c0caf5"
+background = "#1a1b26"
+selection_foreground = "#1a1b26"
+selection_background = "#7aa2f7"
+
+color0 = "#1a1b26"
+color1 = "#f7768e"
+color2 = "#9ece6a"
+color3 = "#e0af68"
+color4 = "#7aa2f7"
+color5 = "#bb9af7"
+color6 = "#7dcfff"
+color7 = "#c0caf5"
+color8 = "#414868"
+color9 = "#f7768e"
+color10 = "#9ece6a"
+color11 = "#e0af68"
+color12 = "#7aa2f7"
+color13 = "#bb9af7"
+color14 = "#7dcfff"
+color15 = "#c0caf5"
+```
+
+All 22 keys are required — this is the same format Omarchy themes and
+`blob_wallpaper`'s pywal-generated `blob-dynamic` theme already use, so
+`omarchy-theme-set` and its app-config templates pick it up with no
+extra work.
+
+### Saving a dynamic palette you like
+
+If a wallpaper's pywal-generated colors are worth keeping permanently,
+dump the currently active theme's `colors.toml` straight into a new
+theme folder instead of typing it out by hand:
+
+```bash
+mkdir -p themes/my-new-theme
+blob_theme --print > themes/my-new-theme/colors.toml
+```
+
+Run `./install.sh` (add `--force` if the theme already exists on disk
+and you're updating it) to deploy new/changed theme folders.
+
+Any theme already installed under `~/.config/omarchy/themes/` or
+bundled with Omarchy itself (`$OMARCHY_PATH/themes/`) shows up
+automatically too — this directory is just for ones you want tracked
+in dotfiles.