ST2110Nic.initialised property

Resolves once the NIC is actually usable: MTL_Init / MTL_Start have completed inside the isox host and an IP address is known (from static config or DHCP). Rejects with the failure reason if any later step in the bring-up errors — including the deep zig-side preflight, which fires asynchronously after preflightComplete has already resolved. Callers that don’t need to await readiness SHOULD still attach a .catch so a late failure isn’t logged as an unhandled rejection by Node; settings.onError is the recommended place to handle that failure for UI surfacing.

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