Customize the html output of theorem div

There are some minor issues of the html output of theorem div. I am using quarto v0.3.114 on mac os.

A minimal example:

::: {#thm-line}

The equation of any straight line, called a linear equation, can be 
written as: $y=ax+b$.

A second par.

:::

See @thm-line.

::: {#thm-line2}

A second theorem.

:::

HTML output:

In the example above:

(1) Sometimes the theorem body begins in a new paragraph (as in Theorem 2), sometimes just following the theorem tag (as in Theorem 1). Not sure whether this is a design choice or not, but it might be better to let the body just follow the theorem tag for consistency.

(2) It's hard to tell the scope of the theorem body. For example, in theorem 1 "A second par" is part of the body, while "See theorem 1" is not.
A possible fix is to put the whole theorem in a box environment. From my experience, many math blogs do that (eg, Terry Tao's blog). Another fix is to italicize the whole theorem/lemma/etc as LaTeX does.

I personally prefer the first fix (i.e., box). A con of the italicize approach is that users may not be able to use the markdown syntax ** for emphasis once the whole texts are italicized. LaTeX solves this problem by using the \emph command, which produces normal texts for emphasis in a italicized environment.

Start with the minimal Markdown example in the issue and inspect how Quarto renders the theorem divs in HTML. Compare the two paragraph behaviors and determine the intended body boundary and presentation, including whether a box or italicized style is required; done means the example has consistent, clearly scoped theorem output.