Truncate gossipsub topic ids to 32 bytes on legacy peers

Truncate gossipsub topic ids to 32 bytes on legacy peers. The escrow accepts the merge cert only when the gitlawb oracle quorum signs a certificate proving that a PR resolving #101 landed on main.

• Tests must stay green on the target branch after merge.
• No new direct dependencies without justification in the PR body.
• If race-eligible, the first valid merge wins; honest losers refunded gas.