Summary

• Moves the ttVAULT_DELETE-specific invariant checks from ValidVault::finalize into VaultDelete::visitInvariantEntry / VaultDelete::finalizeInvariants, following the same pattern established for VaultCreate in the parent branch.
• Extends VaultInvariantData with a beforeMPTs_ vector and a findDeletedShares(mptID) accessor so VaultDelete can locate the deleted MPTokenIssuance without depending on ValidVault's internals.
• The "vault deleted by a wrong transaction type" sentinel in ValidVault is kept — it guards against any non-ttVAULT_DELETE transaction that inadvertently deletes a vault entry. The "vault deletion succeeded without deleting a vault" sentinel (triggered when ttVAULT_DELETE runs but the vault still exists) is now owned by VaultDelete::finalizeInvariants. The delete-specific emptiness checks (no shares, no assets total, no assets available) are also moved to VaultDelete.

Checks moved from ValidVault → VaultDelete

1. afterVaults().empty() — vault was actually deleted (sentinel)
2. findDeletedShares(shareMPTID) found — shares issuance was also deleted
3. sharesTotal == 0 — no outstanding shares at deletion time
4. beforeVault.assetsTotal == 0 — no assets outstanding
5. beforeVault.assetsAvailable == 0 — no assets available

Test plan

• ./xrpld -u Vault,Invariants passes with 437 cases, 0 failures