feat: WriteDeltaEntity_Internal probe (Phase 2 — confirm per-client serial path)

Read-only detour on the per-client delta-write fn (engine 0x6d15c0, sig added to
gamedata). Logs managed thread id + delta-ctx fields (entIdx +0x34, bf_write +0x88,
from/to snapshots +0x90/+0x98) for the first 40 calls. sp_wdeprobe / _off. Goal:
confirm WDE runs serially on the send thread (single tid) vs the parallel pack
workers — decides whether per-client value substitution at WriteFieldList is viable.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>