perf:greedy meshing (#23)

* feat(gameplay): implement greedy meshing for chunk generation

Replace the per-face vertex generation with a greedy meshing algorithm that merges adjacent faces of the same block type into larger quads. Introduce `FaceKey` struct and helper functions (`axis_dir_to_face`, `get_block_safe`, `is_face_culled`, `choose_buf`) to support the new algorithm. Comment out the old `gen_vertices` implementation.

In texture management, rename `m_pbr_texture_array` to `m_normal_texture_array` to reflect its actual usage, and set texture wrap mode to `GL_REPEAT` for both the block and normal texture arrays.

* fix(primitive_data): correct back face texture coordinates and tangents

* fix(texture-manager): correct texture deletion and refactor reload

Make hot_reload private and add public need_reload method. Update UI to call need_reload instead of hot_reload. Fix incorrect use of glDeleteBuffers for normal texture array by using glDeleteTextures.

include/Cubed/texture_manager.hpp

@@ -12,7 +12,7 @@ private:
     GLuint m_texture_array = 0;
     GLuint m_cross_plane_array = 0;
     GLuint m_ui_array = 0;
-    GLuint m_pbr_texture_array = 0;
+    GLuint m_normal_texture_array = 0;
     GLfloat m_max_aniso = 0.0f;
 
     int m_aniso = 1;
@@ -29,6 +29,7 @@ private:
     void init_block();
     void init_ui();
     void init_block_status();
+    void hot_reload();
 
 public:
     TextureManager();
@@ -43,7 +44,7 @@ public:
     const std::vector<GLuint>& item_textures() const;
     // Must call after MapTable::init_map() and glfwMakeContextCurrent(window);
     void init_texture();
-    void hot_reload();
+
     void need_reload();
     void update();
     int max_aniso() const;