run output doesn't get spliced into transcripts #1172
Description
The output of run commands goes to the wrong place during transcript parsing.
Input transcript:
```unison
hi = '(printLine "Hello world!")
```
```ucm
.> add
.> run hi
```
Console output during transcript parsing:
Transcript will be run on a new, empty codebase.
⚠️
Initializing a new codebase in: /home/chris/unison/transcript-53622049952cfb9b.
_____ _
| | |___|_|___ ___ ___
| | | | |_ -| . | |
|_____|_|_|_|___|___|_|_|
Running the provided transcript file...
⚙️ Processing stanza 2 of 3.Hello world!
⚙️ Processing stanza 3 of 3.
💾 Wrote /home/chris/unison/transcript-run.output.md
Note this wrongly includes the "Hello world!" output.
Transcript output produced:
```unison
hi = '(printLine "Hello world!")
```
```ucm
I found and typechecked these definitions in scratch.u. If you
do an `add` or `update`, here's how your codebase would
change:
⍟ These new definitions are ok to `add`:
hi : ∀ (). () ->{IO} ()
Now evaluating any watch expressions (lines starting with
`>`)... Ctrl+C cancels.
```
```ucm
.> add
⍟ I've added these definitions:
hi : ∀ (). () ->{IO} ()
.> run hi
```
This output wrongly omits the "Hello world!"