refactor: use uint64 for L2 sequence numbers in AggregateVerifier

[leopoldjoy]

Summary

• Changes startingL2SequenceNumber and endingL2SequenceNumber from uint256 to uint64 in AggregateVerifier's internal functions (_verifyProof, _verifyTeeProof, _verifyZkProof, _getStartingIntermediateRootAndL2SequenceNumbers)
• Adds explicit uint64() casts at call sites in prove() and verifyProposalProof() where values originate from the uint256 Proposal struct
• This changes the abi.encodePacked journal encoding (8 bytes vs 32 bytes per sequence number), so off-chain TEE / ZK provers must be updated to match

NOTE: Alternatively, we could change Proposal.l2SequenceNumber in Types.sol to uint64 directly, which would eliminate the casts added here but requires updating ~8 interface files and 5 implementation return types (all mechanical, no logic changes).

Test plan

• forge build passes
• All 15 AggregateVerifier tests pass
• Verify off-chain TEE and ZK provers use matching uint64 encoding

[cb-heimdall]

✅ Heimdall Review Status

Requirement	Status	More Info
Reviews	✅ 1/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 0 Sum 1

[MrStudeny]

Nice

Approved review 4003575916 from mw2000 is now dismissed due to new commit. Re-request for approval.