Strange behavior with multi-line prompts

Describe the bug

From a conversation in Discord:

Is this a bug, or me not understanding something about the way prompts work?
let-env PROMPT_INDICATOR = {|| "> " } is the default. But if I change it to:
let-env PROMPT_INDICATOR = {|| "\n> " }
I do get the newline, but the > disappears?
But if I prefix with a space like this, then I get both:
let-env PROMPT_INDICATOR = {|| " \n> " }

How to reproduce

1. let-env PROMPT_INDICATOR = {|| "\n> " }

Notice that you get a prompt w/ a newline, but no >.

Expected behavior

I expected to have a prompt of "> " on a line by itself. (I prefer my prompts always start at the same indentation, regardless of how deep I am into a random file path.)

Or, if there's some additional behavior going on for the various prompts (ex: if some trimming is going on, or multi-line prompts aren't supported), I'd expect to see that in docs. 😊

Screenshots

Configuration

Additional context

No response

Reproduce the behavior with PROMPT_INDICATOR set to a closure returning "\n> ", then compare it with the version prefixed by a space. Trace the Nushell prompt-rendering entry point and existing prompt tests, and consider the behavior complete when a multiline indicator preserves the requested > character or the supported trimming rules are documented.