feat: implement keyboard and mouse input, pattern placement, and HiDPI scaling

Add configurable key bindings (TOML), modifier-aware dispatch, mouse-driven
pattern placement with preview and rotation, cell grid storage/rendering,
and fractional/integer HiDPI scaling. Archive the input-and-placement change
and sync its specs to main specs.

Tests: Hashtable, Config, Grid, Pattern (4/4 pass).

include/tkeyboard.h

@@ -5,7 +5,7 @@
 #include <wayland-client.h>
 #include <xkbcommon/xkbcommon.h>
 
-typedef void (*keyboard_key_handler_t)(uint32_t key, uint32_t state, xkb_keysym_t sym, void *user_data);
+typedef void (*keyboard_key_handler_t)(uint32_t key, uint32_t state, xkb_keysym_t sym, uint32_t mods, void *user_data);
 
 struct keyboard_data {
 	struct wl_keyboard *keyboard;