fix(consensus): use actual round in LocallyProposedValue

[qj0r9j0vc2]

Summary

• Fixed ChannelValueBuilder::build_value() to use the actual round parameter instead of hardcoding Round::new(0)
• This resolves the consensus stall where proposals were rejected with "Ignoring value for round 0, current round: X"

Root Cause

The build_value function signature received a round parameter (prefixed with _ to suppress unused warnings), but the implementation ignored it and always created LocallyProposedValue with Round::new(0). Malachite consensus validates that proposal rounds match the current consensus round, so proposals with round=0 were silently rejected when consensus had advanced beyond round 0.

Changes

crates/consensus/src/host.rs:

• Changed _round: ConsensusRound → round: ConsensusRound (use the parameter)
• Changed LocallyProposedValue::new(height, Round::new(0), value) → LocallyProposedValue::new(height, round, value)

Test Plan

• cargo check -p cipherbft-consensus passes
• cargo fmt -p cipherbft-consensus produces no changes
• Run integration tests to verify consensus makes progress beyond round 0