Add diffusion guide v4 #1890

Job	Run time
cache-pixi-lock / Generate output	1m 7s
Unit tests: windows \| pixi run -e test-latest tests	7m 51s
Unit tests: ubuntu \| pixi run -e test-py313 tests	3m 32s
Unit tests: ubuntu \| pixi run -e test-py311 tests	3m 32s
Unit tests: ubuntu \| pixi run -e test-minimum tests	3m 44s
Unit tests: ubuntu \| pixi run -e test-latest tests	3m 39s
Integration: ${{ matrix.os }} \| pixi run -e ${{ matrix.pixi-environment }} tests-notebooks	0s
TypeChecking: pixi run typing	0s
merge-test-artifacts	0s
	23m 25s

Provide feedback