Add Cursor Cloud specific instructions to AGENTS.md

[goniz]

Adds a ## Cursor Cloud specific instructions section to AGENTS.md with:

• Required environment variables (VK_ICD_FILENAMES, CC/CXX, PATH)
• Build workaround for the 1.2 GB mul_mm.comp.cpp OOM issue on 15 GB VMs
• Test and application run commands verified on Cloud VM
• Lint instructions (pre-commit from mlx/ submodule)

Environment verification

Check	Result
Build (./dev.sh build)	Pass (with OOM workaround for mul_mm.comp.cpp)
C++ tests (DEVICE=cpu ./dev.sh test-cpp)	249 passed, 0 failed
Python tests (DEVICE=cpu ./dev.sh test-py)	699 passed, 13 skipped
Lint (pre-commit run --all-files)	Pass (existing formatting diffs in submodule)
Generation (./dev.sh generate)	Coherent Qwen3-0.6B output on lavapipe

generate_output.log

_{To show artifacts inline, enable in settings.}