Visual keybind builder + scalable awww wallpaper library

[NullifiedSec]

Scope

This branch focuses on practical Hyprland UX: a visual keybind builder and a large-library wallpaper browser backed by awww.

Visual keybind builder

• visual keyboard directly inside the existing Binds page
• SUPER / CTRL / ALT / SHIFT toggles
• live combo preview and existing-bind lookup
• same-submap conflict highlighting
• variable expansion before chord comparison
• one-click Create bind from combo… flow using the existing backup-safe writer
• Vial is used only when available as a read-only source for real keyboard geometry / spacing and layer-0 legends; no firmware writes
• clean built-in logical keyboard fallback when Vial is unavailable

Wallpaper library via awww

• choose and persist a wallpaper library folder
• recursive indexing runs off the GTK main thread
• 48 wallpapers rendered per page to bound GTK widget/decoder pressure
• persistent SSD thumbnail cache at ~/.cache/hyprbinds/wallpapers/
• cache keys include path + file size + modification time, so changed files invalidate automatically
• first page thumbnails are generated before the index is published
• remaining thumbnails warm in the background
• gallery prefers cached JPEG previews and falls back to the original only if the user outruns the cache worker
• click a wallpaper to apply it through awww
• transition, resize mode, output targeting, restore, clear, and rescan remain available
• applying a wallpaper does not trigger a full re-index

Cleanup

The feature branch was rebuilt as one clean commit on top of main; stale Vial-control-center history and files are no longer part of the PR.

Validation

The source was statically reviewed and the gdk-pixbuf savev API was checked against current gtk-rs documentation. A separate local runtime/build pass is still needed before merge.