Liquidation Phase 2 (DEX): stacked on #41

[kgrgpg]

Stacked on #41 (base: feature/liquidation-mechanism).

What

• Introduces DEX-based liquidation path in cadence/contracts/TidalProtocol.cdc: liquidateViaDex(...) and LiquidationExecutedViaDex event.
• Adds DEX guards and config with getters/governance:
  • allowedSwapperTypes allowlist (by Type)
  • dexOracleDeviationBps (max DEX-implied vs oracle deviation)
  • dexMaxSlippageBps, dexMaxRouteHops
  • getDexLiquidationConfig() and setDexLiquidationConfig(...)
• Adds resource-scoped helpers: internalSeize, internalRepay.
• Adds transactions/scripts:
  • pool-management/liquidate_via_dex.cdc
  • pool-management/liquidate_via_mock_dex.cdc (test-only convenience)
  • pool-governance/set_dex_liquidation_config.cdc
  • scripts/tidal-protocol/get_dex_liquidation_config.cdc
• Adds contracts/mocks/MockDexSwapper.cdc for testing; updates flow.json testing alias.
• Tests: liquidation_phase2_dex_test.cdc + updates to test_helpers.cdc, liquidation_phase1_test.cdc.

How it works

1. Quote internal seize amount and cap by maxSeizeAmount.
2. Validate swapper is allowlisted and matches seizeType/debtType.
3. Compute DEX-implied price from quote and compare to oracle; require deviation ≤ dexOracleDeviationBps.
4. Seize collateral (internalSeize) and swap via DeFiActions.Swapper.
5. Optional slippage guard when a quote is provided: enforce slippageBps ≤ dexMaxSlippageBps.
6. Repay debt (internalRepay) and emit LiquidationExecutedViaDex.

Defaults

• allowedSwapperTypes = {} (must be allowlisted by governance)
• dexOracleDeviationBps = 300 (3%)
• dexMaxSlippageBps = 100 (1%)
• dexMaxRouteHops = 3

Diff vs base (#41)

• Modified: cadence/contracts/TidalProtocol.cdc, cadence/tests/liquidation_phase1_test.cdc, cadence/tests/test_helpers.cdc, flow.json
• Added: cadence/contracts/mocks/MockDexSwapper.cdc, cadence/tests/liquidation_phase2_dex_test.cdc, cadence/scripts/tidal-protocol/get_dex_liquidation_config.cdc, cadence/transactions/tidal-protocol/pool-governance/set_dex_liquidation_config.cdc, cadence/transactions/tidal-protocol/pool-management/liquidate_via_dex.cdc, cadence/transactions/tidal-protocol/pool-management/liquidate_via_mock_dex.cdc
• Stats: +456 / -1 across 10 files

Testing notes

• The DEX test deploys and allowlists MockDexSwapper, sets priceRatio to satisfy the oracle deviation guard, funds the MOET vault for swap output, and liquidates via the DEX path.

Risks and considerations

• Governance must allowlist the intended swapper types before use.
• Tune dexOracleDeviationBps and dexMaxSlippageBps to operational preferences.
• MockDexSwapper is test-only and should not be used in production.

Stacking

• Base PR: Liquidation Mechanism: Phases 1 & 2 (core + DEX) #41 (feature/liquidation-mechanism). Merge Liquidation Mechanism: Phases 1 & 2 (core + DEX) #41 first; then this PR can be retargeted to main if desired.

[kgrgpg]

Merged 'feature/liquidation-phase2-merged' into base 'feature/liquidation-mechanism'.

Reason: common Phase 1 liquidation edits were necessary in the base (HF-maximizing fallback, borrower insolvency redemption test, and related helpers). To minimize cherry-picking and keep history coherent, we merged the changes directly into the base branch.

Status: base updated and tests pass locally (one pre-existing rounding-guard assertion remains unchanged). Phase 2 work stays on this branch as-is.