Fix ChunkMesh OpenGL compatibility build errors

[NearDrive]

Motivation

• Prevent build failures on environments where the bundled glad headers are incomplete and do not expose GL_STREAM_DRAW or where glad_glBufferSubData is unavailable.

Description

• In src/voxel/ChunkMesh.cpp add a fallback #ifndef GL_STREAM_DRAW definition and replace the orphan-path glad_glBufferSubData calls with glad_glBufferData uploads to preserve orphaning semantics while avoiding missing-symbol issues.

Testing

• Ran cmake -S . -B build && cmake --build build -j4, which aborted when FetchContent failed to clone GLFW due to network restrictions (CONNECT tunnel failed, response 403), so a full build could not be completed in this environment.

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Codex Task