Profile `release-smaller` sets `panic = "abort"`, which disables uniffi's panic handling

This works, but it doesn't have to be that way, and I just found out by browsing their docs and exploring our `release-smaller` profile.

See https://mozilla.github.io/uniffi-rs/latest/internals/rust_calls.html#panic-handling

Panics can instead just throw `RustCallStatusCode::UnexpectedError`. I want to do a deeper dive into when that could be the right choice here instead of our current "crash the whole process on a Rust panic" approach.

Start by inspecting the `release-smaller` profile and reading the linked UniFFI panic-handling documentation. Investigate whether using `RustCallStatusCode::UnexpectedError` is appropriate here instead of `panic = "abort"`, and define the tests or documented behavior needed to confirm the chosen approach.

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