Escrow Vault Payment Manager

[Kingsman-99]

Description

Some invoice payment flows require holding funds in escrow (locked until delivery confirmation) before releasing them to recipients. The SDK has no escrow primitive — callers use claimable balances ad-hoc without lifecycle management. An escrow vault manager should wrap the create-hold-release pattern using claimable balances with time-lock predicates, coordinating with invoice status to trigger release automatically.

Technical Context

Add src/escrowVaultManager.ts. Builds on src/claimableBalanceFallback.ts and src/predicateBuilder.ts. Adds EscrowVault, EscrowStatus, and EscrowReleaseCondition to src/types.ts. Integrates with src/poller.ts to monitor delivery confirmation events. Release is triggered by src/client.ts confirmDelivery() method. Emits escrowFunded, escrowReleased, and escrowExpired via src/events.ts.

Acceptance Criteria

• EscrowVaultManager.create(invoiceId, amount, asset, holdUntil): Promise<EscrowVault> creates a claimable balance with an absolute-time predicate and returns the vault record
• EscrowVaultManager.release(vaultId, recipientId): Promise<TransactionResult> claims the balance on behalf of the recipient after the hold period
• EscrowVaultManager.getStatus(vaultId): Promise<EscrowStatus> returns the current state: holding | released | expired
• Emits escrowExpired when the hold predicate window closes without release and the SDK detects the balance is claimable by anyone
• Integration test creates an escrow, waits for predicate window (using testnet fast ledger), and asserts escrowReleased event fires after release() call
• All CI checks (npm test, npm run build, ESLint/TypeScript) pass and the branch has no merge conflicts

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