Approximate gas usage per operation (contract design matter…

Approximate gas usage per operation (contract design matters; these are typical ranges):
- Consume on-chain nonce (read + increment + optional event): ~40k–70k gas
- Post audit hash (event-only, no storage write): ~8k–25k gas (+ calldata bytes)
- Add/update session key (new storage slot + bookkeeping): ~80k–120k gas
- Revoke session key (toggle or delete): ~45k–80k gas