ci(docs) Just: setup-just v3 -> v4 #306

Job	Run time
qa (3.13)	30s
qa (3.12)	25s
qa (3.14)	37s
qa (3.11)	25s
qa (3.10)	25s
packages	22s
docs	24s
smoke (root-install)	9s
smoke (sphinx-gp-theme)	13s
smoke (gp-sphinx)	14s
smoke (sphinx-fonts)	12s
smoke (sphinx-autodoc-argparse)	14s
smoke (sphinx-autodoc-typehints-gp)	15s
smoke (sphinx-autodoc-fastmcp)	12s
smoke (sphinx-autodoc-sphinx)	13s
smoke (sphinx-ux-autodoc-layout)	12s
smoke (sphinx-autodoc-pytest-fixtures)	10s
smoke (sphinx-autodoc-api-style)	10s
smoke (sphinx-ux-badges)	13s
smoke (sphinx-autodoc-docutils)	15s
	5m 50s

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