Fix/improve spacing and float clearing for in-content messages/warnings/errors

[Ambient-Impact]

For example, the warning on Skynet (2045 film) on a fairly wide viewport is overlapping the floated infobox and also has no spacing against previous content (in this case a heading, but can be a paragraph, etc.):

• Add spacing against previous
• Clear all floats?

Clearing floats does improve the situation, though it results in a large space between it and the preceding heading now:

It's the less bad of the two options, but we might want to add clear: both to the first heading after the table of contents to fix that: