Brings the post-fork BT411 line forward via a local-path merge (never
touches the BT411 gitea remote): the full audio-fidelity system (engine
AUD*/L4AUD* + audiopresets.cpp + ~600 content wavs + AUDIO_FIDELITY.md),
missiles/rear-fire/HUD/gyro/gait tasks (#66-68), FOGDAY.EGG, and
refreshed context docs -- 91 commits, ~688 files clean.
Only 5 files overlapped the steamification; resolved keeping BOTH:
- L4NET.CPP: took BT411's task-#50 fix (don't close the game listener on
console loss) over the seam's adaptation of the old buggy close; sends
stay on NetTransport_Get().
- L4NETTRANSPORT.cpp: folded BT411's TCP_NODELAY latency fix into
WinsockNetTransport::Connect (the seam already had retry + nonblocking).
- mechmppr.cpp: combined the device_owns_input gating with BT411's
task-#68 look-behind, gating the lookBehind write too.
- .gitignore / CMakeLists.txt / mech4.cpp: trivial / auto-merged
(deviceOwnsInput gating preserved).
Verified: clean build (default + implicitly the Steam TU untouched);
solo front-end mode; loopback MP through the seam (mesh completes, both
tick, replication works, no NODELAY warnings).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>