refactor: reorganize pxl8 into client/src/ module structure

- core/: main entry, types, logging, I/O, RNG
- asset/: ase loader, cart, save, embed
- gfx/: graphics, animation, atlas, fonts, tilemap, transitions
- sfx/: audio
- script/: lua/fennel runtime, REPL
- hal/: platform abstraction (SDL3)
- world/: BSP, world, procedural gen
- math/: math utilities
- game/: GUI, replay
- lua/: Lua API modules

client/src/world/pxl8_world.h

@@ -0,0 +1,38 @@
+#pragma once
+
+#include "pxl8_bsp.h"
+#include "pxl8_gen.h"
+#include "pxl8_gfx.h"
+#include "pxl8_math.h"
+#include "pxl8_types.h"
+
+typedef struct pxl8_world pxl8_world;
+
+typedef bool (*pxl8_texture_rule)(const pxl8_vec3* normal, const pxl8_bsp_face* face, const pxl8_bsp* bsp);
+
+typedef struct pxl8_world_texture {
+    char name[16];
+    u32 texture_id;
+    pxl8_texture_rule rule;
+} pxl8_world_texture;
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+pxl8_world* pxl8_world_create(void);
+void pxl8_world_destroy(pxl8_world* world);
+
+pxl8_result pxl8_world_generate(pxl8_world* world, pxl8_gfx* gfx, const pxl8_procgen_params* params);
+pxl8_result pxl8_world_load(pxl8_world* world, const char* path);
+void pxl8_world_unload(pxl8_world* world);
+
+pxl8_result pxl8_world_apply_textures(pxl8_world* world, const pxl8_world_texture* textures, u32 count);
+bool pxl8_world_check_collision(const pxl8_world* world, pxl8_vec3 pos, f32 radius);
+bool pxl8_world_is_loaded(const pxl8_world* world);
+void pxl8_world_render(pxl8_world* world, pxl8_gfx* gfx, pxl8_vec3 camera_pos);
+pxl8_vec3 pxl8_world_resolve_collision(const pxl8_world* world, pxl8_vec3 from, pxl8_vec3 to, f32 radius);
+
+#ifdef __cplusplus
+}
+#endif