(refactor ?) Xmage handles incorrectly how +1/+1 counters are placed on creatures.

Hello.

I think it's a general issue regarding the way Xmage places +1/+1 counters on creatures, or maybe the way Xmage "sees the player placing +1/+1 counters on creatures."

I will try to explain some issues with examples. I play a lot with +1/+1 counters synergies, so I encouter thoses issues very frequently.

**1) Firt situation with [[Hydroid Krasis]] [[Runadi, behemoth caller]] and [[Loading Zone]].**

I casted Hydroid Krasis for X=30. The mana value of the Krasis is 32, so the Krasis should enter with 28 additionnal +1/+1 counters thanks to Runadi's ability. The Krasis should enters with 58 counters that will be doubled by Loading Zone. Finaly, the Krasis should enter with 116 +1/+1 counters.

But Xmage had it entered with 88 +1/+1 counters instead of 116. It's like if Xmage thought only the "original 30 +1/+1" counters from Krasis were able to be doubled by loading zone, and not the 28 +1/+1 counters added by Runadi.

**2) Second situation with [[Terrasymbiosis]] [Arwen, weaver of hope]] and [[Hydroid Krasis]]**

When I cast any X creature spell (here, Hydroid Krasis) with Arwen and Terrasymbiosis on the battlefield, I will have two triggers from Terrasymbiosis instead of one. (1 trigger for additionnals counters provided by Arwen and 1 trigger for the X +1/+1 counters from the X value of the creature).

**Summary:** My guess is Xmage sees the player placing counters multiple times when there is multiple instances of additionnals +1/+1 counters, or additionnals +1/+1 counters mixed with "enters with X +1/+1 counters".

Any creature entering with X +1/+1 counters and with any instance of additionnal +1/+1 counters, will enter will all the +1/+1 counters placed by the player in a single event. The player needs to add up all the counters the creature will have while entering, then places all those +1/+1 counters in a single time.

You can see that xmage proposes you to choose which "pack" of +1/+1 counters should applies first when the creature is entering. There is a pop up window asking you to choose which effect takes place first (like with Krasis + Runadi). Xmage should rather calculate the total, then makes the creatures entering with the correct number.

What I see now it's that Xmage handles it incorrectly, leading to wrong board state and player's confusion about the incorrect numbers of +1/+1 counters.

Reproduce the two reported scenarios with Hydroid Krasis, Runadi, Loading Zone, Terrasymbiosis, and Arwen to observe counter placement and trigger prompts. Trace the game-engine entry points handling creatures entering with counters and verify the result against the issue's expected totals and single placement event. Done means both examples produce the correct board state without incorrect ordering choices.

Written by the indexing model from the issue text.