* Fixed several of the issues and nits from PR:

* Moved margin between header and file name to header, so when content was scrolled, the header would remain more separate
* Made build-time and runtime overlays better match
* Secondary error <pre> style now uses yellow bg instead of red
* 'Scrollable Header' (see above comment to why this is necessary) but I did increase the max-height from 35% to 50%.
* Fixed header and 'X' button vertical alignment

* Temporary stack margin fix

* Move "N errors" to the top