gameserver: 033b303 dropped cb.broadcasterOwner assignment, UnregisterBroadcasterCallbacks never unregisters anything

[thesprockee]

Found during #44's fix (PR #117). Merge 033b303 dropped the line cb.broadcasterOwner = lobby->broadcaster from RegisterBroadcasterCallbacks (present in parent d339898, added via ba6b5f0). Since then, UnregisterBroadcasterCallbacks (callback_unregistration.cpp:11) never actually unregisters anything in production — it only Clear()s the local registry struct, leaving the real EchoVR::BroadcasterUnlisten call unreached.

Per this repo's devolution-ratchet lesson: this is exactly the "which commit unwired it" pattern — found, not guessed. Restoring the line changes what the game thread does during its own Unregister() path, so it's scoped as its own fix/PR rather than folded into #44 (which fixes a different, off-thread race on the same registry).

[thesprockee]

Correction: this is fixed/found alongside PR #118 (#44), not #117 (which is this issue itself — typo in the original body).

[thesprockee]

Ordering dependency found by the Opus review of #118 (PASS verdict, issue #44's fix merged as dfca641): today this registry's broadcasterOwner field is only ever assigned in tests (the production assignment was dropped by merge 033b303), so the unregister branch that calls into the game (callback_unregistration.cpp:11) is dead in production — the pre-fix race was two threads both writing zeros via Clear(), which has no visible effect. If this issue (#117, restoring the dropped broadcasterOwner assignment) lands BEFORE #44's fix was in place, the latent race would have gone live: BroadcasterUnlisten would run off-thread against the non-atomic chain walk in ReceiveLocalEvent, risking memory corruption. #44 is now merged (main_thread_handoff marshals the unregister call onto the game thread), so this ordering constraint is satisfied — #117 is safe to pick up now.

[thesprockee]

Fixed by c19f472 (landed directly on main due to a branch-tracking misconfiguration in the implementer's worktree — no PR exists, but the fix got a full retroactive Opus review at the same rigor as a normal merge gate: PASS, independently verified including mutation testing that confirms the new tests actually fail without the fix). Restored cb's broadcasterOwner recording via GameServer::RecordBroadcasterOwner, called before first listen (gameserver.cpp:943). Traced both routes into UnregisterAllCallbacks — the game's own CNSLobby::Unregister path and the graceful-shutdown path added by #44's main_thread_handoff — both confirmed to reach BroadcasterUnlisten on the correct thread. just verify green, independently reproduced in a scratch worktree.