Add diffusion guide v4 #1874

Job	Run time
cache-pixi-lock / Generate output	15s
Unit tests: ubuntu \| pixi run -e test-py311 tests	3m 40s
Unit tests: ubuntu \| pixi run -e test-py313 tests	3m 30s
Unit tests: ubuntu \| pixi run -e test-latest tests	3m 35s
Unit tests: ubuntu \| pixi run -e test-minimum tests	3m 38s
Unit tests: windows \| pixi run -e test-latest tests	10m 6s
Integration: ${{ matrix.os }} \| pixi run -e ${{ matrix.pixi-environment }} tests-notebooks	-1s
TypeChecking: pixi run typing	-1s
merge-test-artifacts	0s
	24m 42s

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