fix: Restrict auto list conversion to paragraphs

[Mulgyeol]

Description

When users type list markers ("1." or "-/+/*") at the beginning of a block, BlockNote automatically converts it into a list.
Previously, this conversion would trigger in any block with inline content, including headings and custom blocks.
This was disruptive when users wanted to start headings or other blocks with numbers or list markers.

This change restricts the auto-conversion to list blocks to paragraph blocks only,
preserving these inputs in other block types as plain text.

Fixes #1710

Changes

• Modified the input rule condition in NumberedListItemBlockContent.ts to check for paragraph blocks specifically
• Modified the input rule condition in BulletListItemBlockContent.ts to check for paragraph blocks specifically

Testing

The following scenarios should be tested:

1. In a heading block:

   • Type "1." at the start
   • Expected: Text remains as "1." without converting to a numbered list
   • Type "-" or "+" at the start
   • Expected: Text remains as is without converting to a bullet list

2. In a paragraph block:

   • Type "1." at the start
   • Expected: Block converts to a numbered list item
   • Type "-" or "+" at the start
   • Expected: Block converts to a bullet list item

3. In a custom block (like alert block):

   • Type "1." or list markers (-/+/*)
   • Expected: Text remains as is without converting to any type of list

[vercel]

@Mulgyeol is attempting to deploy a commit to the TypeCell Team on Vercel.

A member of the Team first needs to authorize it.

[nperez0111]

@Mulgyeol this might also be an issue for people using custom blocks who want that automatic conversion.

I suggest instead to disallow the conversion in elements we know we don't want it in: headings for example.

Or, to somehow flag which elements should have this behavior or not with something like the group they are apart of

[Mulgyeol]

Thanks for the feedback! @nperez0111

Yeah, I see your point — restricting auto-conversion in non-paragraph blocks might cause inconvenience for users who expect that feature.
So, I reverted the previous approach and now restrict auto list conversion only in heading blocks, allowing it for other block types for more flexibility.

I figured that heading blocks are explicitly intended for titles, and users starting with "1." or "-" in those contexts are typically not trying to create a listso this felt like a safe and targeted change to apply directly.

As a follow-up, I'd love to explore adding a more flexible system using flags or metadata per block type, so custom blocks can opt in or out of this behavior explicitly. I'll look into contributing that in a future PR!

Let me know if you have further thoughts!