feat(noctalia): use wallpaper-derived light themes

[CollieIsCute]

What changed

• force Noctalia's wallpaper-derived palette to light mode
• replace local Alacritty, Ghostty, and Kitty templates with Noctalia's built-in adapters
• enable built-in theming for Alacritty, btop, Ghostty, GTK 3/4, Kitty, Qt, and WezTerm
• use Noctalia as the only Arch Linux terminal palette while preserving existing Catppuccin themes on macOS and non-Arch Linux
• add the official Arch adw-gtk-theme and qt6ct packages, remove the stale GTK dark/Kvantum overrides, and manage the minimal qt6ct palette selection
• leave Fish, tmux, Zellij, Lazygit, and cursor themes unchanged because Noctalia has no built-in adapter for them

Why

The previous Arch setup loaded Catppuccin fallbacks before Noctalia overlays and carried three local copies of terminal templates. That produced two palette owners and duplicated templates now shipped by Noctalia. This change makes Noctalia the single owner for officially supported Arch targets and lets it derive a light palette from the current wallpaper.

adw-gtk-theme remains the GTK 3 base theme used by Noctalia's generated CSS. Plain qt6ct is sufficient for the installed Qt 6 apps; the KDE-patched AUR variant is intentionally not used.

Validation

• noctalia config validate home/dot_config/noctalia/config.toml — valid; seven unrelated existing widget migration warnings remain
• confirmed all eight selected IDs with noctalia theme --list-templates
• rendered Arch, macOS, and Ubuntu chezmoi template branches; non-Arch platforms retain existing Catppuccin themes
• luac -p passed for rendered WezTerm and Hyprland configs
• Ghostty's config validator passed
• ran Noctalia's four terminal post-hooks in an isolated temp home; checksums confirmed no main-config drift
• targeted chezmoi cat renders passed
• git diff --check passed

The full distro apply remains delegated to the existing GitHub Actions workflow.