src/relay/relay-frame-decoder.ts and src/main/ssh/relay-frame-decoder.ts
were 264 identical lines apart from one default: the relay logs decode
faults to stderr when no handler is supplied, the SSH side stays silent.
Two copies of framing logic is exactly where a wire-format fix lands in one
and not the other.
The decoder's contract and buffer already live in src/shared, so the class
joins them there. The relay keeps a thin subclass that supplies its stderr
default, preserving behaviour for the call sites that omit onError. The
SSH copy is deleted and relay-protocol.ts points at shared directly.
Verified: pnpm typecheck, 102 tests across the 9 framing/backpressure/
handshake suites, and `pnpm build:relay` for all six platform targets plus
the WSL hook relay — the standalone bundle has no new dependencies.
Neil