fix: validator address

[alxdca]

Summary

• Register the dedicated accounts.validator address as the L3 rollup validator.
• Generate the L3 node config with accounts.validator.privateKey instead of accounts.l3owner.privateKey.

Why / Context

• L3 parent-chain funding and staking already target accounts.validator.
• The L3 rollup deployment and generated node config still pointed at accounts.l3owner.
• That mismatch can leave the L3 runtime unable to post assertions as the expected validator, matching the NOT_VALIDATOR symptom and preventing L3 delayed inbox consumption.