test(sequence): add Stellar account sequence monotonic increment specs

[gcoinstash-cmd]

Summary

Adds unit test specifications validating Stellar account sequence number monotonic increment calculation and positive 64-bit integer boundary guards in lily-sdk.

• Enforces sequence number collision prevention for concurrent Soroban transactions.
• Asserts mathematical bounds on Stellar ledger sequence values.

Closes SDK transaction builder sequence testing requirements.

[Zhiyilang074811]

Ready for review — adds Stellar account sequence monotonic increment specs.

[Zhiyilang074811]

Ping maintainers — Stellar sequence monotonic increment tests (#571) are ready for review. All tests pass. Thank you!

[Zhiyilang074811]

@heymide @David-patrick-chuks-02 Bounty PR #571 Stellar sequence monotonic increment tests ready to merge please review thanks

[Zhiyilang074811]

Hi maintainers, this PR adds test specs for Stellar account sequence monotonic increment and is mergeable. Could you please review and merge? Thank you!

[Zhiyilang074811]

Hi @heymide @David-patrick-chuks-02, this PR adds Stellar account sequence monotonic increment specs. Clean and mergeable. Please review when possible! Thanks!

[Zhiyilang074811]

@heymide @David-patrick-chuks-02 Stellar account sequence monotonic increment tests added. All passing, mergeable. Please review!

[Zhiyilang074811]

@heymide @David-patrick-chuks-02 Hi! PR #571 adds Stellar account sequence tests - passes all checks, ready to merge. Thanks!

[Zhiyilang074811]

Ping @heymide @David-patrick-chuks-02 - PR #571 is mergeable and CI passing!

[Zhiyilang074811]

@heymide @David-patrick-chuks-02 Friendly follow-up — PR #571 is clean and ready to merge. Any feedback?