Quantum Layer Separation in Original Bitcoin: Authorization, Proof-of-Work, Residual State, and Ordering

This paper argues that quantum risk in original Bitcoin is layer-specific rather than protocol-uniform. Using the November 2008 pre-release witness as its primary corpus, it separates authorization, proof-of-work, residual-state accounting, and timechain ordering. The clearest Shor-sensitive surface is authorization, where public-key signatures govern spending authority. Proof-of-work belongs to a different problem class: hash-target search, where Grover-class advantage changes search economics without becoming key recovery. Residual spendable state and accepted ordering are not themselves cryptographic secrets, though they may be affected indirectly if authorization or proof-of-work assumptions change. The paper does not claim that original Bitcoin is quantum-proof or provide a production post-quantum migration design. It argues instead that migration discussion should begin only after the protocol layers have been separated.