What
The footer is the line of hints shown under the box where you type. Its hint can now carry an extra piece of text, shown dimmed after a · separator. That extra text appears only when it fits in the space available, and the footer now tells the hint how much room a wrapped line has. This is part of wider rework of the footer layout.
Why
The footer hint can carry more information when your terminal is wide enough, without spilling onto another line when it is not.
Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.
The writer flagged doubt
What supplies the extra text, and when the hint is shown at all, is not settled.