fix(bridge): reject adversarialResilience >= validatorCount

[crazywriter1]

Summary

• Enforce adversarialResilience < validatorCount when updating the validator set, so certificate claims always require weight ≥ 1
• Reject certificate proofs when requiredWeight == 0 (defense-in-depth for misconfigured state)
• Update validator-set unit and fuzz tests for the strict f < n invariant

Previously f == n (or n == 0) was accepted by config validation. That made validatorCount - adversarialResilience == 0, so an empty aggregate signature (weight = 0) satisfied the claim check. This is an admin misconfiguration footgun, not a default-deployment drain path — shipped configs use f < n — but the contract allowed the bad state and should not.

Test plan

• forge test --match-contract BridgeUpdateValidatorSetTest -vv
• forge test --match-path test/Bridge.t.sol

[crazywriter1]

Hi @abresas @poszu friendly ping for a review when you have a moment.

This PR enforces adversarialResilience < validatorCount and rejects certificate proofs when requiredWeight == 0, closing the f == n misconfiguration footgun where an empty aggregate signature could pass.

I verified locally with:

• forge test --match-contract BridgeUpdateValidatorSetTest -vv
• forge test --match-path test/Bridge.t.sol

Happy to adjust anything if you’d prefer a different validation approach. Thanks!