fix(tholos): verify balance deltas for incoming token transfers (#164)

[xtep103]

Overview

Verifies balance deltas for incoming token transfers during assertion creation (assert_outcome) and disputes (dispute) in contracts/tholos, recording actual received tokens and protecting resolve and finalize payouts against deadlocks caused by fee-on-transfer tokens.

Related Issue

Closes #164

Changes

contracts/tholos

• [MODIFY] contracts/tholos/src/lib.rs
  • Added balance delta checks around incoming token transfers in assert_outcome and dispute.
  • If actual received tokens are less than requested, records the received amount into assertion.bond in persistent storage. Rejects zero/negative received amounts with Error::InvalidBondAmount.
  • Clamped payouts in finalize (assertion.bond.min(contract_balance)) and resolve ((assertion.bond.saturating_mul(2)).min(contract_balance)) to prevent transfer failure panics when contract balances are constrained by transfer deductions.
• [MODIFY] contracts/tholos/src/test.rs
  • Added FeeToken test fixture simulating configurable fee-on-transfer mechanics.
  • Added unit test test_fee_on_transfer_token_dispute_resolves_without_deadlock confirming assertions with fee tokens can be disputed and resolved without balance underflow.
  • Added unit test test_fee_on_transfer_token_finalize_resolves_without_deadlock confirming undisputed assertions with fee tokens finalize successfully.
  • Added unit test test_zero_received_transfer_rejected ensuring 100% fee transfers that deliver 0 tokens are rejected.

Verification Results

running 79 tests
test test::fee_token::test::test_fee_token_transfer ... ok
test test::test_fee_on_transfer_token_dispute_resolves_without_deadlock ... ok
test test::test_fee_on_transfer_token_finalize_resolves_without_deadlock ... ok
test test::test_zero_received_transfer_rejected ... ok
...
test result: ok. 79 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

cargo test --workspace --locked: 189 tests passed (79 tholos, 110 tholos-v2), 0 failed
cargo clippy --workspace --all-targets --locked -- -D warnings: 0 warnings
cargo fmt --check: OK

Acceptance Criteria	Status
Balance deltas verified around token transfer calls in assert_outcome & dispute	✅ Implemented and verified
Actually received amount recorded in storage if short; 0-amount rejected	✅ Tested with Error::InvalidBondAmount
resolve / finalize clamped to available balance to prevent deadlock	✅ Tested and verified
Unit tests covering fee-on-transfer resolution & zero-transfer rejection	✅ All tests passing

[xtep103]

Closing duplicate PR in favor of #180, which has been updated with the clean, verified commit history and full test suite.

[collinsezedike]

@xtep103 closing this as a duplicate of #180, same diff, opened 20 minutes apart. Review findings are on #180, let's continue there.