feat: add OpenGL abstraction layer with RAII resources

- Replace window class with cbt::opengl::context
- Add buffer resource (VBO, EBO, UBO, SSBO) with move semantics
- Add texture resource with format/type enums and filtering
- Add descriptor_set for Vulkan-style resource binding
- All resources use RAII with proper cleanup

deps/Findimplot3d.cmake

@@ -0,0 +1,52 @@
+# ==============================================================================
+# Find implot3d
+# ==============================================================================
+# Builds ImPlot3D from the bundled sources in deps/implo3d/.
+#
+# Targets provided:
+#   implot3d::implot3d - The ImPlot3D library target
+#
+# Variables set:
+#   implot3d_FOUND       - TRUE if implot3d is available
+#   implot3d_LIBRARIES   - The implot3d library target (implot3d::implot3d)
+#   implot3d_INCLUDE_DIR - Include directories for implot3d
+#
+# Configuration (set before find_package):
+#   IMPLOT3D_BUILD_DEMO - Include demo sources (default: ON)
+# ==============================================================================
+
+if (DEFINED _FINDIMPLOT3D_INCLUDED)
+    return()
+endif()
+set(_FINDIMPLOT3D_INCLUDED TRUE)
+
+option(IMPLOT3D_BUILD_DEMO "Include ImPlot3D demo sources" ON)
+
+set(_implot3d_source_dir "${CMAKE_CURRENT_LIST_DIR}/implo3d")
+
+if (NOT EXISTS "${_implot3d_source_dir}/implot3d.cpp")
+    message(FATAL_ERROR "implot3d sources not found at '${_implot3d_source_dir}'")
+endif()
+
+if (NOT TARGET imgui::imgui)
+    message(FATAL_ERROR "implot3d requires imgui::imgui to be available before find_package(implot3d)")
+endif()
+
+add_subdirectory("${_implot3d_source_dir}" "${CMAKE_BINARY_DIR}/_deps/implot3d-build" EXCLUDE_FROM_ALL)
+
+if (NOT TARGET implot3d::implot3d)
+    message(FATAL_ERROR "implot3d: target implot3d::implot3d was not created")
+endif()
+
+set(implot3d_FOUND      TRUE)
+set(implot3d_LIBRARIES  implot3d::implot3d)
+get_target_property(_implot3d_inc implot3d INTERFACE_INCLUDE_DIRECTORIES)
+set(implot3d_INCLUDE_DIR "${_implot3d_inc}")
+
+if (_implot3d_inc AND TARGET implot3d)
+    set_target_properties(implot3d PROPERTIES
+        INTERFACE_SYSTEM_INCLUDE_DIRECTORIES "${_implot3d_inc}"
+    )
+endif()
+
+set(IMPLOT3D_LICENSE_FILE "${_implot3d_source_dir}/LICENSE" CACHE FILEPATH "Path to ImPlot3D license file")