Complex return types

[Nintorac]

Having a bit of problem with complex types, maybe it's a bit too early for the extension template, but I'm learning a lot anyway.

---

https://github.com/Nintorac/duck_midly/blob/main/src/functions.rs#L25-L161

Here's the type annotation I've landed so far, finding it very difficult to construct the object, is there any guidance on how to maybe do this in a better way? Maybe construct it in arrow first and then pass that back to DuckDB?

With my manual construction efforts I'm seeing some strange outputs.

1. Inactive Union Fields Contain Garbage Data

• Issue: Inactive union fields contain uninitialized memory values instead of being null
• Evidence: Test failure shows event.kind.midi.message.pitch_bend.bend has garbage data
  in a note_on event
• Impact: Inactive fields return random values like 5e-324 instead of null/empty values

2. Inconsistent Field Visibility

• Issue: Direct field access works but parent struct access doesn't
• Evidence: event.kind.midi.channel works, event.kind.midi shows None
• Impact: Creates confusion about data availability and struct state

Tests here highlighting the issues

FWIW this could just be my very..very basic understanding of rust and a whole lotta AI slop thats landed me here.

Slightly related to some of the chat in #6