Make Dispatcher::dispatch_requested pub and extract abort-cascade handling
into a pub handle_abort method so the WebSocket handler can feed deserialized
EventEnvelopes directly to the shared Dispatcher without a QUIC Connection.
CallConnection gains a new_overlay_only(identity) constructor (Option A) that
holds the Layer 2 overlay, PendingRequestMap, and resolved bearer Identity
without a QUIC Connection; identity() reads the stored field for the non-QUIC
case. compose_root_env uses the new identity() accessor for both paths.
The existing QUIC path (CallAdapter, CallClient, run_loop, handle_stream) is
unchanged — outgoing client methods guard on connection().is_none().
glm-5.2
ef53a03589