Keep the position. Draw against it

20/// @title Ketro lending pool.
21/// @notice Lenders deposit pUSD and hold ERC-4626 shares; borrowers lock Polymarket outcome
22///         tokens and draw pUSD against them.
23///
24/// @dev The pool *is* the vault — there is no separate LP token contract. Being a standard
25///      ERC-4626 is what lets yield aggregators consume the pool directly, which the PRD
26///      names as a distribution goal.
27///
28///      Debt is stored scaled by `borrowIndex` rather than as an absolute figure, so accruing
29///      interest is a single index update instead of a loop over every loan.
30///
31///      Liquidation deliberately does not pay the caller. The seized collateral and bonus go
32///      to the treasury, because the price feed is operated by the protocol itself: paying
33///      the liquidator would give whoever holds the oracle key a direct, immediate profit
34///      from writing a false price. See ADR 0001.
35contract LendingPool is ERC4626, AccessControl, Pausable, ReentrancyGuard {
36    using SafeERC20 for IERC20;
37 
38    bytes32 public constant RISK_ADMIN_ROLE = keccak256("RISK_ADMIN_ROLE");
39    bytes32 public constant LIQUIDATOR_ROLE = keccak256("LIQUIDATOR_ROLE");
40    bytes32 public constant PAUSER_ROLE = keccak256("PAUSER_ROLE");
41 
42    struct Loan {
43        address borrower;
44        uint256 tokenId;
45        uint256 collateralAmount;
46        /// @dev Debt divided by `borrowIndex` at the time it was taken on.
47        uint256 principalScaled;
48        uint64 openedAt;
49        bool active;
50    }
51 
52    MarketRegistry public immutable REGISTRY;
53    IPriceOracle public immutable ORACLE;
54    ICollateralAdapter public immutable ADAPTER;
55 
56    IInterestRateModel public interestRateModel;
57    address public treasury;
58 
59    /// @notice Cumulative interest index, WAD-scaled, starting at 1e18.
60    uint256 public borrowIndex = ProtocolMath.WAD;
61    uint64 public lastAccrualTs;
62 
63    /// @notice Sum of every loan's `principalScaled`.
64    uint256 public totalBorrowsScaled;
65    /// @notice Protocol's accumulated share of interest, in pUSD. Excluded from `totalAssets`.
66    uint256 public reserves;
67 
68    uint256 public protocolFeeBps = 1_500; // 15%
69    uint256 public tvlCap;
70    /// @notice Fraction of a loan repayable in one liquidation, in bps.
71    uint256 public closeFactorBps = 5_000; // 50%
72    /// @notice Below this health factor the whole loan may be closed at once.
73    uint256 public fullLiquidationHealthFactor = 0.9e18;
74 
75    /// @notice Trailing window used to price new loans.
76    uint64 public borrowPriceWindow = 30 minutes;
77    /// @notice Maximum age of an oracle observation before it is refused.
78    uint64 public maxPriceAge = 30 minutes;
79 
80    /// @notice Delay on moving protocol reserves to an outside address.
81    uint256 public constant RESERVE_WITHDRAWAL_DELAY = 2 days;
82 
83    /// @notice How long a queued action stays executable once its delay has elapsed.