Retain native packets and verify status casts in protocol CI and isolated server

Retain the actual native C++ packet corpus and test Slow/Seal casts through the real server handlers, so the client issue #1 (closed) evidence can be reproduced without a dated client-build directory or NX assets on the server test machine.

NativeStatusSkills checks all four variants at ranks 1/20: learned/unlearned and insufficient-MP cases, exact payment, actual monster status values/IDs, no attack damage, target caps, Slow range boundaries and real scheduler expiry. Seal chance remains unchanged; retries observe successful application without certifying its probability distribution. Sole-boss status is logged rather than imposed as an unverified gameplay rule.

The corpus contains 72 actual attack packets, eight incoming Player::damage packets and eight status casts, with checksums and generating client/binary provenance. A validation-only CI job compiles Java, runs existing offline regressions, verifies hashes and checks the production parser. Its exact commands passed in a network-disabled Java 8 container. GitLab CI lint passed.

The full disposable server/database run passed 1,403 assertions using the committed corpus; all eight status cases and eight actual incoming HP cases passed. No campaign account, population consumption or shared EXP is used. No production server logic changes beyond dependency !84.

Related to client issue #1, which stays open. No full skill/input/damage-formula certification, merge or deployment.

Paired client: https://gitlab.mapplestrudel.com/idanc/mapplestrudel-client/-/merge_requests/17