NativeConnectorReceivesFromExternalManagedProvider -> NativeConnectorReceivesFromExternalProvider:
CULTMESH_NATIVE_EXTERNAL_ENDPOINT's peer is no longer necessarily the C#
managed provider now that Cut 5 adds a TypeScript one on the same lane; the
env var name stays, since it names the endpoint, not the peer.
Add ManagedConnectorReceivesFromExternalProvider, gated by the same env var:
dials an external provider with the plain managed connector and no
ValidateProviderCertificate (so acceptance runs on the endpoint's own
cert-sha256 pin alone, like an ordinary consumer), and prints the received
frame's CultMeshRealtimeWireProtocol re-encoding as hex for the harness's
golden-bytes comparison against the TypeScript peer's own encoding.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>