Incorrect position when new file/dir are added after last dir

[fangzhen]

Suppose the following file tree with two files: test/foo/bar, test/baz. Treemacs display it like this:

    test/
      foo/
        bar
      baz

Then add a dir $ mkdir test/foz, we would expect:

    test/
      foo/
        bar
      foz/
      baz

But actually got:

    test/
      foo/
      foz/
        bar
      baz

I'm using treemacs from melpa with version 20240613.2014.

In treemacs--determine-insert-position, when the new node is added after last dir, position of new node is calculated as after position of the last dir, but not its descendants.

[stale]

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