feat(darwin-breeze): unify theme colors across KDE, Helium, T3 Code and Ghostty

Move the Darwin Breeze Dark color scheme and global theme into a stow
package. build.py generates the Helium, T3 Code and Ghostty themes from
DarwinBreezeDark.colors, and apply.sh rebuilds and applies them, so the
colors are edited in one place.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

darwin-breeze/README.md

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+# Darwin Breeze
+
+Breeze for KDE Plasma 6 in the macOS dark system colors, with Helium, T3 Code
+and Ghostty themed from the same colors.
+
+Only the colors change. Breeze still draws the widgets and the title bar, and
+the window buttons stay on the right.
+
+- Selection and focus rings use the macOS blue, `#007AFF`.
+- The title bar has the same color as the toolbar below it, so the two read as
+  one strip.
+- When a window loses focus, its selection turns gray, as on macOS.
+- Errors, warnings, success text and links use Apple's system red, orange,
+  green, blue and purple.
+
+## Install
+
+From `~/.dotfiles`:
+
+```sh
+stow darwin-breeze helium
+./darwin-breeze/apply.sh
+```
+
+`apply.sh` regenerates the app themes, applies the global theme, hides the
+line under the title bar, turns off the wallpaper accent color and publishes
+the T3 Code theme. Restart Helium afterwards; T3 Code switches on its own.
+
+## Changing colors
+
+The color scheme is the only place colors are defined:
+
+```
+.local/share/color-schemes/DarwinBreezeDark.colors
+```
+
+Edit it, then run `./darwin-breeze/apply.sh` again. Everything else follows:
+
+| App | How it gets the colors |
+| --- | --- |
+| Qt / KDE apps | the color scheme itself |
+| GTK apps | Breeze GTK, which `kde-gtk-config` syncs from the scheme |
+| Tray icons in `tray-icons/` | `ColorScheme-Text`, recolored by Plasma |
+| Helium | `.local/share/helium-themes/`, generated by `build.py` |
+| T3 Code | `t3/darwin-breeze.json`, generated by `build.py` and published with `t3 theme set` |
+| Ghostty | `.config/ghostty/themes/`, generated by `build.py` |
+
+The generated files are committed so that `stow` alone gives a working setup;
+don't edit them by hand.
+
+## T3 Code notes
+
+- T3 Code ignores symlinked theme files, so the theme isn't stowed;
+  `apply.sh` publishes a copy into `~/.t3/userdata/themes/`.
+- Every slot of the T3 theme maps to a role in the color scheme (see `t3()` in
+  `build.py`), so a new slot or a different mapping is a change there, not a
+  hand-edited color.
+
+## Helium notes
+
+- Helium loads the theme from `~/.local/share/helium-themes/darwinbreeze`
+  through `--load-extension` in `helium/.config/helium-browser-flags.conf`.
+- In Helium's compact layout the active tab and the toolbar segments on either
+  side share one theme color, so the toolbar is the same color as the tab
+  strip and inactive tabs are drawn lighter, as Dolphin does.
+- Chromium tags its output as sRGB and KWin shows it with a gamma 2.2 curve,
+  which lifts dark grays (40 becomes 44). `build.py` writes pre-compensated
+  values for Helium and T3 Code (both Chromium), so the theme files say 35
+  where the screen shows 40.
+- Under Settings → Appearance the theme must be Classic, not GTK or QT.
+
+## When the colors don't show up
+
+- In System Settings → Colors, take the accent color from the color scheme. A
+  custom accent, or one taken from the wallpaper, replaces the blue.
+- Use the Plasma style called "Breeze". "Breeze Dark" and "Breeze Light" carry
+  their own colors, so panels and popups ignore the scheme.
+- GTK apps follow the scheme only with the Breeze GTK theme. Flatpak apps also
+  need `org.gtk.Gtk3theme.Breeze` installed.