Highlight syntax errors in minimap

Currently, when I have a syntax error in a large file (even a small file) it can be hard to see. For example, in my most recent experience, a single curly-brace was underlined with red. I usually resort to building on the command-line for this, so it will give me a line number, but it seems like there should be a better way to know the code is in a bad state, and identify where to go first.

Start by tracing how syntax-error diagnostics from the language server reach the editor and whether the existing red underline path exposes locations usable by the minimap. Confirm the minimap's highlighting behavior and define done as making syntax-error locations visibly identifiable there, including the single-brace case described in the issue.

Written by the indexing model from the issue text.