Revert "Bump sphinx from 8.2.3 to 9.1.0"

[adamtheturtle]

Reverts #2820

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Note

Reverts recent documentation tooling upgrades to restore previous versions in pyproject.toml.

• Set sphinx from 9.1.0 back to 8.2.3
• Set doc8 from 2.0.0 back to 1.1.1

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