Implement missing specification locks and proofs

[secsovereign]

Description

Add formal verification proofs for uncovered consensus rules.

Context

We have 176+ proofs, but there are still consensus rules that could benefit from formal verification.

Acceptance Criteria

• Identify consensus rules without proofs
• Implement proofs for identified rules
• Verify proofs pass

Technical Details

• Files: src/**/*.rs (add #[spec_locked] blocks)
• Reference: docs/FORMAL_VERIFICATION_PLAN.md
• Skills: Formal verification, Z3, Rust, Bitcoin consensus

Difficulty

• Intermediate

Priority

• P1 (High)

Getting Started

1. Review docs/FORMAL_VERIFICATION_PLAN.md
2. Identify rules needing proofs
3. Study existing spec-lock proofs
4. Implement new proofs
5. Run: cargo spec-lock verify