docs: RE the CalcDelta output field-index list format (CUtlVector<int>)

Completes the Option D spec: the delta output list is a CUtlVector<int> {count@+0,
sizeAndFlag@+4 with 0x80000000 heap bit, inline[4]/heapptr@+8}. Injecting the hooked
field = a standard push-back respecting the inline(<=4)/heap split. All four Option D
pieces now RE'd — implementation is mechanical, pending live-client validation + the
Windows global-load sig.

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