test: buy-then-sell round-trip returns correct XLM to seller

[soomtochukwu]

Summary

I added an integration test for a sequential buy-then-sell round-trip starting from a fresh creator at supply 0. After buying one key and selling it immediately, the seller’s net proceeds match the sell-step price minus creator and protocol fees, and supply returns to 0.

I only tackled issue #560. No contract logic or unrelated tests were changed.

What the test asserts

• Fresh creator supply is 0 before the buy
• Buy succeeds (supply 1, key balance 1); buyer payment = buy quote total_amount (price + fees); fee ledgers move by quote fees
• Sell quote net = price - creator_fee - protocol_fee and matches compute_fees_for_payment
• Sell succeeds; supply and key balance return to 0; sell fee ledgers increase by quote fees
• Seller XLM in (quote net) is less than buyer XLM out (fees make the round-trip non-free)

Related Issue

Closes #560

Test plan

cargo test -p creator-keys --test buy_sell_round_trip_proceeds
# test test_buy_then_sell_round_trip_returns_correct_xlm_to_seller ... ok

Scope

I only resolved #560.

[Chucks1093]

Nice work @soomtochukwu . I will merge this now and hit up when I create more issues on accesslayer.

Thanks for contributing

[soomtochukwu]

Nice work @soomtochukwu . I will merge this now and hit up when I create more issues on accesslayer.

Thanks for contributing

... looking forward to it :)