`cases` block needs surrounding parens in Doc only

[aryairani]

Describe and demonstrate the bug

> builtins.mergeio

  Done.

x.doc = {{
```
cases x -> 1 -- fails
```
}}

  Loading changes detected in scratch.u.

  I got confused here:



  I was surprised to find an end of input here.

x.doc = {{
```
(cases x -> 1) -- ok
```
}}

  Loading changes detected in scratch.u.

  + x.doc : Doc2

  Run `update` to apply these changes to your codebase.

Screenshots If applicable, add screenshots to help explain your problem.

Environment (please complete the following information):

• unison version: 3c5e994'
• OS/Architecture: macOS 26.0.1 arm

Additional context is this related to #5473 ?

[sellout]

Did you run into this issue outside of a transcript originally?

I can replicate the behavior in a transcript, but as soon as I try to minimize the test case (e.g., a parser unit test) the block parses exactly as I’d expect. If you’ve only seen this in a transcript, maybe that’s where the issue lies (although the transcript runner just takes each block and loads it like a file, so it doesn’t really have a distinct codepath).

[sellout]

Ah, I can replicate it in a scratch file too. But still odd that unit tests, etc. work.