Heading escape "API" object documentation

[minijackson]

What version of myst-parser are you using?

4.0.1

What version dependencies are you using?

Sphinx 8.2.3, docutils 0.21.2

What operating system are you using?

Linux

Describe the Bug

When adding heading in an "object" directive, the heading escape outside of object content, at the end of the page for level 1 headings, and before the object for level 2 headings.

Expected Behavior

If I understood correctly, #711 says that those headings should be transformed into rubrics instead of sections.

To Reproduce

Compile this page:

# Title

:::{py:data} foo
bar
# baz level 1
wunderbar
:::

:::{py:data} foo2
bar
## baz level 2
wunderbar
:::

:::{py:data} foo3
bar
# baz level 1 bis
wunderbar
## sub-baz level 2
wunderbar
### sub-baz level 3
wunderbar
:::

Observe the following result

In pseudoxml format

    <section ids="title" names="title">
        <title>
            Title
        <index entries="['single',\ 'foo\ (built-in\ variable)',\ 'foo',\ '',\ None]">
        <desc classes="py data" ...>
            <desc_signature _toc_name="foo" ...>
                <desc_name classes="sig-name descname" ...>
                    foo
            <desc_content>
                <paragraph>
                    bar
        <section ids="baz-level-2" names="baz\ level\ 2">
            <title>
                baz level 2
            <paragraph>
                wunderbar
        <index entries="['single',\ 'foo2\ (built-in\ variable)',\ 'foo2',\ '',\ None]">
        <desc classes="py data"...>
            <desc_signature _toc_name="foo2" class="" ...>
                <desc_name classes="sig-name descname" ...>
                    foo2
            <desc_content>
                <paragraph>
                    bar
        <index entries="['single',\ 'foo3\ (built-in\ variable)',\ 'foo3',\ '',\ None]">
        <desc classes="py data" ...>
            <desc_signature _toc_name="foo3" ...>
                <desc_name classes="sig-name descname" ...>
                    foo3
            <desc_content>
                <paragraph>
                    bar
    <section ids="baz-level-1" names="baz\ level\ 1">
        <title>
            baz level 1
        <paragraph>
            wunderbar
    <section ids="baz-level-1-bis" names="baz\ level\ 1\ bis">
        <title>
            baz level 1 bis
        <paragraph>
            wunderbar
        <section ids="sub-baz-level-2" names="sub-baz\ level\ 2">
            <title>
                sub-baz level 2
            <paragraph>
                wunderbar
            <section ids="sub-baz-level-3" names="sub-baz\ level\ 3">
                <title>
                    sub-baz level 3
                <paragraph>
                    wunderbar