Sound variable merge in HLIL results in incorrect decompilation

Version and Platform:

• Binary Ninja Version: 6.0.10501-dev
• Edition: Ultimate
• OS: OSX
• OS Version: 26.5.2
• CPU Architecture: M3

Bug Description:
Merging two variables used as i in consecutive for loops results in semantically incorrect code when merging in the wrong order. When merging the second variable into the first, it loses that variable's first initialization. There might be another bug here that the initialization is not inside the for loop's initialization slot. Merging the second variable into the first seems to work how I expect it to.

Steps To Reproduce:

1. Merge i_1 in the second for loop with i from the first
2. See error

Expected Behavior:
I expect to see the initialization of i to zero before/inside the first for loop regardless of variable merge order (or for this behavior to be documented plus a warning when merging in the incorrect order, and probably not labeling them as sound merges).

Screenshots/Video Recording:
i merged with i_1, correctly clears value to zero before each loop

i_1 merged with i, doesn't initialize i to zero

Binary:
phoenix index traces logarithmically

Reproduce the issue in Binary Ninja's HLIL using the provided “phoenix index traces logarithmically” binary. Compare merging i_1 into i with the reverse order, then inspect the resulting initialization around both for loops. Done means the merged result preserves initialization to zero regardless of merge order, or the behavior is documented with an appropriate warning.