Reset and pair notification gates and connected recipients

RE-748. Reproduce with python3 scripts/analyze_qvm_client_notifications.py; validate with cargo xtask test-group notifications. See the machine report.

Recovered complete6369 and6439 over65 fixtures including null first pointer, in-use/client gates, empty/negative counts and mixed connection states. Client stride6336 selects recipients while entity stride880 constructs callback arguments. The loops themselves make no external state mutation.179736/180087 callback internals, positive counts beyond the four-slot fixture, and live networking remain open.

No original executable/full VM/native world collision or rendering runs. Supplied callback/native responses and fixture domains remain explicit; complete macOS/Linux Rust/Bevy/Solari gameplay remains open.