whitespace should not be required after =

```
* item[3].linkId ="Practitioner.qualification:certificate3-community"
```
gives the following error:
```
Sushi: error mismatched input '="Practitioner.qualification:certificate3-community"' expecting {'units', '='} (00:10.0780)
```

This can be fixed by adding a space after the equals.

Whitespace should not be required here.

Start by reproducing the reported FSH input and inspect the parser entry point that handles assignment expressions, using the shown mismatched-input error as the guide. Done means the same input parses successfully without requiring whitespace after `=` while existing assignment syntax continues to work.

Written by the indexing model from the issue text.