MTU Clamping (Bug 8a): Clamp link MTU signalling in LINKREQUEST packets
when forwarding through transport node, matching Python reference impl.
Without this, TCP endpoints negotiate 8192-byte segments that exceed the
V3's 1064-byte HDLC buffer, causing silent truncation and permanent
resource transfer stalls at ~70%.
Fixed MTU declaration (Bug 8b): Set FIXED_MTU=true on TcpInterface so
Transport uses HW_MTU for clamping decisions.
Oversized frame detection (Bug 8c): Track truncated HDLC frames and
drop them with a diagnostic log instead of silently delivering corrupt
data to Transport.
Echo-back prevention (v1.0.10): Track which TCP client originated each
inbound frame and skip that client in send_outgoing() to prevent
flooding TCP buffers.
Register local client interface: Enable Transport forwarding of
announces, link packets, and proofs to TCP clients.
Document all discovered microReticulum bugs in MICRORETICULUM_BUGS.md.
MODE_ACCESS_POINT unconditionally blocks announce broadcasts in
Transport::outbound(), preventing local TCP clients from discovering
each other. Changing to MODE_GATEWAY allows announces to flow through
send_outgoing() which broadcasts to all connected clients.
Root cause: receiver's announce was stored in announce_table but never
rebroadcast on LocalTcpInterface, so sender could never find a path.
