FrameAccumulator state machine in framing.rs holds partial prefix/payload
bytes across non-blocking receive() calls — a frame split across TCP
segments no longer desyncs the stream (read_exact previously discarded
partially-consumed bytes on WouldBlock). receive_bridge_inputs now drains
all ready frames per tick (capped) instead of exactly one, covering input
batches + atlas requests in the same window.
Review hardening: EOF mid-frame escalates to Disconnected like clean EOF
(peer died with a truncated stream) instead of logging an Io error every
tick. Tests: frame split inside prefix / inside payload, multi-frame
drain, mid-frame-EOF disconnect. Corrupt-stream escalation tracked as
T-1072.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>