fix(markdown): Correctly render loose lists with blank lines

[anish-devgit]

Problem

Previously, Rich rendered all Markdown lists as "tight" lists, even when items were separated by blank lines (loose lists). This squashed list items together, ignoring the intended vertical spacing defined in the CommonMark spec.

Solution

I updated the ListItem class in rich/markdown.py to respect the hidden attribute provided by the markdown-it-py parser.

• Logic Update: When ListItem.on_child_close processes a child element, it now checks if that child is explicitly marked as "visible" (not token.hidden).
• Rendering: If it is visible (indicating a loose list), a single blank line (Text(" ")) is appended to the renderable elements.
• Regression Tests: I updated tests/test_markdown.py and tests/test_markdown_no_hyperlinks.py to reflect the corrected, spaced-out rendering. This ensures no regressions for standard (tight) lists while fixing the output for loose lists.

Example

Input:

1. Item 1

2. Item 2

Before:
1 Item 1
2 Item 2

After:
1 Item 1

2 Item 2

Linked Issue
Fixes #3907