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/tpointer.h

@@ -5,6 +5,8 @@
 #include <wayland-cursor.h>
 
 
+typedef void (*pointer_button_handler_t)(uint32_t button, uint32_t state, double x, double y, void *user_data);
+
 struct pointer_data {
 	struct wl_cursor_theme *cursor_theme;
 	struct wl_pointer *pointer;
@@ -12,10 +14,18 @@ struct pointer_data {
 	struct wl_cursor *cursor;
 	struct wl_cursor_image *cursor_image;
 	struct wl_buffer *cursor_buffer;
+
+	double x;
+	double y;
+
+	pointer_button_handler_t button_handler;
+	void *user_data;
 };
 
 extern const struct wl_pointer_listener pointer_listener;
 
 void pointer_init_cursor(struct pointer_data *pointer_data, struct wl_compositor *compositor, struct wl_shm *shm);
 
+void pointer_set_button_handler(struct pointer_data *pointer_data, pointer_button_handler_t handler, void *user_data);
+
 #endif