Custom signing runtime

@seams/wallet/runtime is for hosts that supply the platform around the signing engine. It is a lower-level integration than SeamsWeb.

The entrypoint exports createSigningRuntime, createSigningRuntimeStatePorts, and types for the runtime configuration, services, state ports, UI dependencies, and warm-session UI ports.

The runtime receives platform services through ports: interfaces your host implements. These cover:

• authentication.
• time and randomness.
• HTTP transport.
• durable records and secure secrets.
• signer cryptography.
• runtime-specific UI.

Choose one RuntimePortsKind and provide the complete matching RuntimePorts branch. Validate raw host data before constructing those ports. A custom runtime also manages secure storage, cancellation, lifecycle restoration, and checks for user presence. Use the browser SDK unless you intend to manage these responsibilities.

Read architecture and origin and iframe boundaries first.