Expression syntax highlighting doesn't seem to respect comments

**Describe the bug**

Here, this line should appear as a comment:

**To Reproduce**

Here's the text:

```yaml
update-rust-toolchain:
runs-on: ubuntu-latest
# Don't run on forks; will attempt to create a PR into the fork...

# if: ${{ !github.event.pull_request.head.repo.fork }}
```

**Extension Version**
`v0.25.6`

Start by reproducing the issue with the YAML example in the report using extension version v0.25.6, then inspect the extension's syntax-highlighting implementation and any related tests. Done means the commented expression line is highlighted as a comment without breaking expression highlighting elsewhere; no specific file or test is named in the report.

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