Add LGProtocol as a pinned submodule and consume its KVMFR protocol
definitions throughout the client, host, IDD, OBS, and profiler.
Keep Looking Glass framebuffer helpers local while removing duplicated
protocol headers and migrating users to KVMFR-scoped types.
Extend the clipboard target boundary with ordered prefix delivery.
Pass up to four queued LGMP stream records to the Helper ring in one
operation, apply state only to the accepted prefix, and retain the
remaining suffix for exact retries.
The channel holds its write lock across the prefix and emits one pipe
doorbell per stream window instead of one per record.
