[test] Foundry fork tests for CharonLiquidator (all Venus markets + slippage edge cases)

[obchain]

Context

Before a single mainnet tx, the liquidator contract must pass fork tests against real BSC state. Fork tests pin a block number, fork the chain in-memory, and execute the full flow with real reserves — the closest we get to mainnet without spending gas.

Scope

• contracts/test/CharonLiquidator.t.sol
• Fork setup: pin a block number where a known Venus position is liquidatable
• Happy path: full liquidation, assert profit > 0, assert flash-loan repaid in full
• Slippage path: force a bad minAmountOut, assert tx reverts (no state change)
• Authorization: call executeLiquidation from non-owner, assert revert
• Multi-market: parameterize test to run across top-5 Venus vTokens (BNB, USDT, USDC, BTCB, ETH)
• Foundry forge snapshot to lock gas costs

Acceptance criteria

• forge test --fork-url <bsc-rpc> passes all tests
• Gas snapshot committed (.gas-snapshot) and checked in CI
• Slippage failure mode covered by an explicit test
• Owner-only gate covered by an explicit test
• Tests run in < 60 seconds locally against a reachable BSC RPC

References

• PRD section 7c (Testing)
• Foundry fork tests: https://book.getfoundry.sh/forge/fork-testing

[obchain]

Superseded — Foundry fork-test suite shipped in feat/25-foundry-fork-tests.