Value method
Returns a Pointer<Char> for text using the next anonymous ring-buffer slot.
Anonymous slots cycle modulo slotCount, so older anonymous strings may be overwritten.
If key is provided, delegates to ValueAt instead.
Implementation
Pointer<Char> Value(String text, [String? key]) {
if (key != null) return ValueAt(key, text);
final slot = _StringAnonIndex;
_StringAnonIndex = (_StringAnonIndex + 1) % slotCount;
_ensureStringSlotExists(slot);
return _writeStringToSlot(slot, text);
}