test: add full coverage for DeltaResolver

[eversoluna]

Summary

Adds full branch coverage for DeltaResolver.sol by updating MockDeltaResolver and DeltaResolver.t.sol.

The new tests exercise:

• positive and negative delta paths in _getFullDebt / _getFullCredit
• early-return behavior in _take and _settle
• OPEN_DELTA and CONTRACT_BALANCE handling in amount mapping helpers
• wrap / unwrap balance checks and revert paths

Notes

• Tests only, no production code changes
• Uses unlock context to safely observe transient deltas
• Ensures all deltas are cleared before returning to satisfy PoolManager invariants