docs(python): add pre-release PyPI warning #88

Job	Run time
test (Python 3.9)	30s
typecheck (mypy --strict)	20s
test (Python 3.11)	18s
test (Python 3.13)	25s
duplication	10s
lint (ruff)	19s
Hawk daemon contract snapshot	9s
test (Python 3.10)	21s
security (pip-audit)	29s
test (Python 3.12)	20s
build (sdist + wheel)	15s
	3m 36s

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