I feel like Kagi was just asking "Impress us" and OP misunderstood the assignment by actually building a solid project and handling edge cases that no one cared about.
Anyways thanks for writing this up OP, it was an interesting read and I am a Kagi customer so I liked learning about them.
they actually did not... the original requirement said "a minimal, terminal-inspired email client" and "take inspiration from existing terminal email tools like aerc, mutt". This is nowhere near them, not even close.
Not sure why OP makes no mention of this in their blog post - perhaps they thought those parts were unimportant? In which case I am not surprised at the results.
The project was well made, but my read on it was that they wanted to be shown something interesting. Even if it wasn't as well made of polished, I got the impression they would have preferred something "fun" or imaginative.
Anyways thanks for writing this up OP, it was an interesting read and I am a Kagi customer so I liked learning about them.