[JuliaLowering] Avoid analyzing variables 'owned' by outer closures (#60646)
I should have noticed this when reviewing #60567 . The justification /
comments added by Claude here were very misleading. They explain that
these values are different but not why.
That said, the confusion here is a bit understandable. The `is_capt`
naming is a probably overloaded: "captured anywhere" is very different
than "introduced in an outer function". Might be worth revisiting in a
future re-factor.