feat: add Logics/Propositional/NaturalDeduction/*#91

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thomaskwaring:nj-deduction

Commits on Oct 8, 2025

define proposition, theory
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definition and basics of natural deductions
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substitution
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Commits on Oct 9, 2025

extensions of theories
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docs
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Commits on Oct 11, 2025

scope grinds, lemmas

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