Institutional Vault Release v2.6.4

Institutional Vault: v2.6.4
Policy Nodes: v8.26.6
NATS: v2.6.4
configmap-init: v0.1.0

Policy Nodes:
- Canton signing recognizes TransferInstruction Reject and Withdraw outcomes alongside ExecutedTransfer.
- The Canton gRPC client backs off keepalive intervals to comply with server policy.
- The Canton faucet driver propagates errors when an upstream call returns a non-200 response.