Justify articles to a fixed line width

Your platform shows articles in a fixed-width text column. Write a function that lays out a list of articles and returns every output line in order, as one flat list.

def format_articles(articles: list[str], max_width: int) -> list[str]: ...

Rules

• Each article is a string. Its words are the maximal runs of non-whitespace characters.
• Format each article separately. A line never holds words from two articles, so each article starts on a new line.
• Pack words greedily: put as many words on a line as fit with at least one space between neighbours.
• Every output line has exactly max_width characters.
• Full justification: spread the extra spaces over the gaps between words as evenly as possible. When they do not divide evenly, the gaps on the left get one more space each.
• Left justification: the last line of each article, and any line that holds only one word, uses single spaces between words and is padded with spaces on the right.
• An article with no words produces no lines.

Constraints

• 1 <= max_width <= 100
• 0 <= len(articles) <= 10^4, total characters up to 10^6
• Every word is at most max_width characters long.

Example 1

articles  = ["the quick brown fox jumps over the lazy dog", "hello world"]
max_width = 12
output    = ["the    quick",
             "brown    fox",
             "jumps   over",
             "the lazy dog",
             "hello world "]

The second article starts on its own line, and its last line is padded on the right.

Example 2

articles  = ["a b c d e"]
max_width = 6
output    = ["a  b c",
             "d e   "]

The first line has 3 letters and 3 spaces for 2 gaps, so the left gap gets 2 spaces and the right gap gets 1.

Reconstructed from the reported question; details may differ from what interviewers ask.