School Idol Slots not updated when idolizing

I don't know if this was an oversight or if it's intended, but when idolizing a card its slots don't increment+1. For example, an unidolized SR has 2 slots, but when idolized (at least with a copy of the same card) it increases to 3. Right now, it stays at 2 slots as if you just idolized the card with a seal. I would want to assume that most cards are idolized via copies, and thus the slots should naturally increase and only be changed manually if you manually use seals.

Start by locating the idolization logic and tracing how it distinguishes using a duplicate card from using a seal. Verify the current slot value for both paths, then confirm the intended copy-based increment and identify the relevant regression coverage before making changes.

Written by the indexing model from the issue text.