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/gfx/pxl8_anim.h

@@ -0,0 +1,56 @@
+#pragma once
+
+#include "pxl8_gfx.h"
+#include "pxl8_types.h"
+
+typedef struct pxl8_anim_state_machine pxl8_anim_state_machine;
+
+typedef struct pxl8_anim {
+    u32* frame_ids;
+    u16* frame_durations;
+    u16 frame_count;
+    u16 current_frame;
+    f32 time_accumulator;
+
+    bool loop;
+    bool playing;
+    bool reverse;
+    f32 speed;
+
+    pxl8_anim_state_machine* state_machine;
+
+    void (*on_complete)(void* userdata);
+    void (*on_frame_change)(u16 frame, void* userdata);
+    void* userdata;
+} pxl8_anim;
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+pxl8_anim* pxl8_anim_create(const u32* frame_ids, const u16* frame_durations, u16 frame_count);
+pxl8_anim* pxl8_anim_create_from_ase(pxl8_gfx* gfx, const char* path);
+void pxl8_anim_destroy(pxl8_anim* anim);
+
+pxl8_result pxl8_anim_add_state(pxl8_anim* anim, const char* name, pxl8_anim* state_anim);
+u16 pxl8_anim_get_current_frame(const pxl8_anim* anim);
+u32 pxl8_anim_get_current_frame_id(const pxl8_anim* anim);
+const char* pxl8_anim_get_state(const pxl8_anim* anim);
+bool pxl8_anim_has_state_machine(const pxl8_anim* anim);
+bool pxl8_anim_is_complete(const pxl8_anim* anim);
+bool pxl8_anim_is_playing(const pxl8_anim* anim);
+void pxl8_anim_pause(pxl8_anim* anim);
+void pxl8_anim_play(pxl8_anim* anim);
+void pxl8_anim_render_sprite(const pxl8_anim* anim, pxl8_gfx* gfx, i32 x, i32 y, i32 w, i32 h, bool flip_x, bool flip_y);
+void pxl8_anim_reset(pxl8_anim* anim);
+void pxl8_anim_set_frame(pxl8_anim* anim, u16 frame);
+void pxl8_anim_set_loop(pxl8_anim* anim, bool loop);
+void pxl8_anim_set_reverse(pxl8_anim* anim, bool reverse);
+void pxl8_anim_set_speed(pxl8_anim* anim, f32 speed);
+pxl8_result pxl8_anim_set_state(pxl8_anim* anim, const char* name);
+void pxl8_anim_stop(pxl8_anim* anim);
+void pxl8_anim_update(pxl8_anim* anim, f32 dt);
+
+#ifdef __cplusplus
+}
+#endif