[contracts] vBNB fork coverage absent with no tracking reference — #121 fix will have no fork regression guard

[obchain]

Refs #53

File: contracts/test/CharonLiquidatorFork.t.sol

Problem:
vBNB (native collateral redemption) is excluded from the fork test suite because issue #121 (vBNB native path broken) is not yet resolved. This is acceptable for now. However, the test file contains no skipped stub, no TODO comment, and no reference to #121. When #121 is resolved, the developer fixing it has no fork test scaffold to run, and no reminder that fork coverage is required.

This repeats the pattern that led to issue #123 (fork tests absent for the full liquidation flow) — a gap that this very PR is intended to close.

Impact:
vBNB is one of the highest-TVL Venus markets. A fix to #121 that is incorrect (wrong WBNB wrap path, wrong balance accounting) would merge without any fork-level validation. The existing unit tests do not exercise the native-BNB redeem path.

Fix:
Add a skipped stub in CharonLiquidatorFork.t.sol:

// TODO(#121): vBNB native collateral path — add fork coverage once #121 is resolved.
// vBNB address: 0xA07c5b74C9B40447a954e1466938b865b6BBea36
// vBNB redemption returns native BNB; requires WBNB wrap before exactInputSingle.
function test_fork_vBNB_SKIP() public {
vm.skip(true);
}

This makes the gap explicit and searchable.

[obchain]

blocked on contract port: the vBNB -> WBNB wrap branch from the #121 fix (upstream commit b189447 on feat/12) has not yet reached feat/25-foundry-fork-tests. adding a vBNB regression test now would assert behaviour the contract on this branch does not yet implement. deferred until the contract change lands here.

[obchain]

Fixed on feat/25-foundry-fork-tests (39d18cb): CharonLiquidatorFork.t.sol now contains test_fork_vBNB_nativeCollateral_SKIP, a vm.skip(true) scaffold documenting the wrap-to-WBNB and cold-wallet profit-sweep assertions expected once #121 lands. Body names vBNB/WBNB addresses and the four-step fixture the fix-author needs to build.