v0.7.4 — fix mining-serve state-root mismatch at tip (#15)
compute_proofs now builds a separate prover from storage instead of
shallow-cloning the main prover's tree. The old path shared Rc<RefCell>
pointers — operations on the clone mutated visited flags and children
pointers on shared nodes, corrupting the main prover for the next block
apply. Fresh prover from storage = no shared state = clean applies.
Full Changelog: v0.7.3...v0.7.4