Fix calculate_content_widths when inline boxes immediately follow a hard/explicit newline

[nicoburns]

LLM Contributions: Bug identified and code generated with Devin Ultra.

Fix calculate_content_widths when an inline boxes immediately follows a hard/explicit newline. They were previously incorrectly counted as being before the newline because the "Mandatory Break" is only set on the character following the line break. This change mirrors what the line-breaking is already doing into the content width calculation.

Changelog

Added

• Fix calculate_content_widths when an inline boxes immediately follows a hard/explicit newline. They were previously incorrectly counted as being before the newline.

[DJMcNab]

Unfortunately, I don't have enough context to review this. It does look a bit suspect - the whitespace_advance(prev_atom) looks like it might be happening twice?

[DJMcNab]

Suggested change

	///
	/// The mandatory break used to be detected via the boundary flag on the text
	/// atom *after* the break, so inline boxes between the newline and that atom
	/// were attributed to the line *before* the break, under-reporting the max
	/// content width. In Blitz this caused inline-block links following a `<br>`
	/// to wrap inside a shrink-to-fit container even though they fit on one line.