docs+gamedata: force-resend confident mechanism (hook WriteFields +0x70, path-agnostic)

Deeper RE: WriteDeltaEntity_Internal builds the field-index list via TWO paths
(change-tick filter: changeTick>baselineTick; and value-compare CalcDelta), both
feeding the same CUtlVector<int> to the encode fn at vtable slot 14 (+0x70). So the
correct path-agnostic hook is the consumer (+0x70), not CalcDelta (+0x40): sorted-insert
the hooked field's flattened-leaf index into its list arg for issuer+hooked-entity.
Adds the serializer-singleton global (0xac4ae0) to gamedata. Mechanism now fully
RE-confirmed; implementation is mechanical.

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