hy3

hy3 (HYprland + i3) is a custom Hyprland layout registered via
hl.layout.register that emulates the i3/sway window-management
behaviors Hyprland's built-in layouts (dwindle, bstack) do not
provide:

- Directional window movement (mod+shift+dir) that respects a real,
persisted n-ary tree, matching sway's `move left/right/up/down`.
- Persistent per-container split orientation (sway's `splith`/`splitv`):
a container remembers its orientation and every window that lands in
it (opened or moved in) inherits it until explicitly toggled.
- Sway-correct focus traversal with wrapping, and cross-monitor
hand-off for both `move` and `focus` past a workspace edge.

Behavioral spec: notes/sway-spec.md (movement/insertion/closure) and
notes/dual-monitor.md (cross-monitor), both verified against sway 1.12.
Tabbed and stacked layouts are deliberately out of scope.

The `hl` API is provided at runtime by Hyprland (>= 0.50, which
introduced the custom layout API); this rock only installs the Lua
module. Requiring the module registers the layout as 'lua:hy3' and
exposes an `_G.hy3dbg` debug helper. A compat `layout` module is
also installed so `require("layout")` keeps working for configs
written against this repo's original layout.lua.