Add checked-addition helper for quote accumulator math

[Chucks1093]

Summary
Add checked-addition helper for quote accumulator math

Scope

• add reusable checked-addition helper used in quote accumulator paths\n- integrate helper where accumulator overflow checks are needed\n- add focused tests for helper behavior

Acceptance Criteria

• scoped change is implemented with no unrelated file churn
• docs/tests are updated where applicable
• contributor can validate the outcome locally

Contributor coordination: if you pick this up, reach out in Telegram for updates or clarification: https://t.me/accesslayerorg

[EmeditWeb]

@EmeditWeb has applied to work on this issue as part of the Stellar Wave Program's 4th wave.

I'd like to fix this . Thank you

ℹ️ Repo Maintainers: To accept this application, review their application or assign @EmeditWeb to this issue.

[drips-wave]

Congratulations, @EmeditWeb! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on April 29, 2026.

🧑‍💻 @EmeditWeb: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

Warning

When opening a PR, please link it to this issue to ensure it gets tracked accurately. Points are awarded when this issue is marked as completed by the maintainer.

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🌊 Happy Wave 🌊

[drips-wave]

This issue has been marked as completed by a Drips Wave moderator for @EmeditWeb as part of the Stellar Wave Program's 4th Wave 🥳

Moderator's reason: [Auto-assessed] The contributor successfully implemented the requested checked-addition helper and integrated it into the quote accumulator logic as specified. The PR also includes appropriate unit tests for both the helper and the response formatter, directly addressing the acceptance criteria with no maintainer objections.

😎 @EmeditWeb: You earned 100 Points for completing this issue! After the current Wave ends, you'll be eligible for a percentage of the Wave's reward pool based on the percentage of total points you've earned. Learn more here.

🧑‍💻 Repo maintainers: How'd the contributor do? Leave a review to share your experience working with them.

ℹ️ Note: This issue was marked complete via moderation. Points were issued even though the GitHub issue remains open.