Binary I/O (#5): all 12 remaining encoding/binary calls are
legitimate (zero-alloc spot-reads, random-access into game blobs).
Copy-paste handlers (#8): loadCharacterData/saveCharacterData helpers
now cover standard blob patterns.
Also upgrades saveCharacterData to send doAckSimpleFail on oversize
payloads and DB errors, and migrates handleMsgMhfSaveScenarioData
to the improved helper.
handleMsgSysOperateRegister returned without sending an ACK when the
payload was empty, causing the client to softlock waiting for a response.
Send doAckBufSucceed with nil data on the early-return path to match
the success-path ACK type.
Also update tests to expect error returns instead of panics from
unimplemented Build/Parse stubs (matching prior panic→error refactor),
and mark resolved anti-patterns in docs.
Covers 13 identified anti-patterns across error handling, architecture,
concurrency, and code organization with severity ratings and
recommended refactoring priorities.
