Key points:\n- restore the tests tree removed by bc47e6e\n- capture current editor workspace, scene, and docs reshuffle changes\n- keep local cloud.nvdb resources ignored from this commit
- Add assert() bounds check to GetBackBuffer() to catch invalid indices
- Include <cassert> in D3D12SwapChain.cpp
- Update test_swap_chain.cpp to use reference return type
- Mark InvalidIndex test as DISABLED (assert aborts on invalid index)
- Update get-back-buffer.md documentation
