MSG_MHF_GET_EXTRA_INFO (0xA6) and MSG_MHF_GET_COG_INFO (0xC3) had
Parse() returning NOT IMPLEMENTED. The dispatch loop treats any Parse
error as a hard drop — no ACK is ever sent, so the client waits
indefinitely and effectively soft-locks when entering the G-rank
Workshop or Master Felyne (Cog) screens.
Fix: parse AckHandle (the only field we can confirm from the protocol)
and respond with doAckBufFail so the client receives a well-formed
buf-type ACK with error code 1. The client's fail branch for these
requests exits cleanly without reading response fields, avoiding the
read-past-EOF crash that an empty success ACK would cause.
The full response format for both packets is still unknown; a complete
implementation requires further RE. The TODO comments mark the gap.
Fixes#180.
Add // stub: unimplemented to 70 empty game-feature handlers and
// stub: reserved to 56 protocol-reserved slots in handlers_reserve.go,
making them discoverable via grep. Add docs/unimplemented.md listing all
unimplemented handlers grouped by subsystem with descriptions.
