strange `break-align-symbols` behaviour

[Werner LEMBERG]

In December I asked the question below on the 'lilypond-user' list
(https://lists.gnu.org/archive/html/lilypond-user/2023-12/msg00014.html),
alas, without an answer – I try again, this time on 'lilypond-devel'.
I'm also attaching the image for completeness.

Please help.


    Werner


======================================================================


Please consider this example.

```tex
\version "2.25.11"

music = {
  c'1
  \tempo "T-note" c'1
}

\markup { time-signature }
{
  \override Score.MetronomeMark.break-align-symbols =
    #'(time-signature)
  \music
}

\markup { time-signature, key-signature }
{
  \override Score.MetronomeMark.break-align-symbols =
    #'(time-signature key-signature)
  \music
}

\paper {
  ragged-right = ##f
}
```

I don't understand why the addition of `key-signature` to the
`break-align-symbols` list makes 'T-note' left-align to the bar line —
there is no key signature at this point, right?  IMHO, the correct
behaviour would be that 'T-note' is still aligned to the note.

What am I missing?  Or is this a bug?