Add diffusion guide v4 #1899

Job	Run time
cache-pixi-lock / Generate output	1m 5s
Unit tests: ubuntu \| pixi run -e test-minimum tests	3m 39s
Unit tests: windows \| pixi run -e test-latest tests	9m 14s
TypeChecking: pixi run typing	0s
Unit tests: ubuntu \| pixi run -e test-py311 tests	3m 40s
Unit tests: ubuntu \| pixi run -e test-py313 tests	3m 33s
Unit tests: ubuntu \| pixi run -e test-latest tests	3m 26s
Integration: ${{ matrix.os }} \| pixi run -e ${{ matrix.pixi-environment }} tests-notebooks	-1s
merge-test-artifacts	0s
	24m 36s

Provide feedback