Add helper for asserting total supply matches sum of all holder balances in test fixtures

[Chucks1093]

Summary

A key invariant of the contract is that total supply always equals the sum of all individual holder balances. Tests that modify supply or balances should verify this invariant after every state change. A shared assertion helper makes this check easy to add to any test.

Scope

• Add assert_supply_equals_holder_sum(env, creator_id, holders: Vec<Address>) test helper
• Reads total supply and each holder's balance, sums balances, asserts equality
• Panics with a descriptive message showing total supply and computed sum if they differ
• Use the helper in existing buy, sell, and transfer tests

Acceptance Criteria

• Helper correctly identifies a supply/balance mismatch
• Panic message shows both expected and actual values
• Helper passes when supply and holder sum match exactly
• Used in at least three existing test cases

ETA: 12 hours

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Coordinate on Telegram

[Godsmiracle001]

@Godsmiracle001 has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

can i fix this

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Godsmiracle001 to this issue.

[kodinaka30-ship-it]

@kodinaka30-ship-it has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hello Maintainer,

I would like to work on this issue because supply/balance invariant assertions are essential for catching subtle state bugs. I can implement assert_supply_equals_holder_sum, ensure it panics with a clear mismatch message showing both values, and integrate it into at least three existing buy, sell, and transfer test cases.

Please kindly assign

ℹ️ Repo Maintainers: To accept this application, review their application or assign @kodinaka30-ship-it to this issue.

[grantfox-oss]

🦊 GrantFox — @Godsmiracle001 has been assigned to this issue as part of the Official Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #492)
2. Your PR will be reviewed by the accesslayerorg maintainers

Good luck! Track your progress on GrantFox.

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Congratulations, @Godsmiracle001! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

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This issue has been completed by @Godsmiracle001 as part of the Stellar Wave Program's 6th Wave 🥳

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[BWM0223]

PR #496 submitted — supply holder sum helper. Payment wallets ready: ETH 0xeaCAb48a4bfA0CED0e668c166615927115655594 | SOL C3MD2yfWYebB8FYXpq6ooqzU5GCQB1bDxbDhQf1JfiCW | BTC bc1qtmlgtvg7xgv0zry3ct90elp3y7d3ffdutk4e2f