test: show fee mints can leave held shares below the protected amount

[jayeshy14]

Adds test/FeeFloorBreach.t.sol, which shows that fee mints can leave shares held to maturity below their protected amount.

settleTerm asks the controller for the shortfall first and then mints the performance fee against the high-water mark. Nothing caps that fee at the cushion above the floor. The management fee accrual has the same gap. Each test brings the vault to a state where NAV meets the promise before fees and then checks navPerShare after settlement.

Test	Setup	Reported shortfall	navPerShare after fees
stepRatchet_endsBelowProtected	STEP90 steps protection to 1.125, maturity at 1.13	0	1.1046
tippLock_endsBelowLock	LOCKED80 locks 1.2, maturity at 1.21	0	1.1694
chargedWhileShortfallReported	Fixed90 term 2 protects 1.35, ends at 1.30	0.05/share	1.2803, fee still minted
staleMarkChargesEarlierTermGains	fee off in term 1 leaves the mark at 1.00, then turned on	0	1.2916 vs 1.35
pushesFlooredVaultBelowProtected	Fixed90 at exactly 0.90 at maturity, 200 bps management fee	> 0, all from the fee	0.8824

The tests use the existing mock legs and executor and set leg values directly to reach each maturity NAV, so they cover the fee arithmetic and not the market path to it.

They assert current behaviour, so they are expected to fail once the fix lands. The fix should turn them into invariant checks: navPerShare after fees stays at or above the protected amount (the TIPP lock included), and the reported shortfall matches the real one.

forge test passes on this branch (non-fork suite), and forge fmt --check is clean.