fix(markdown): render blank lines for loose lists

Updates ListItem to respect the 'hidden' token attribute from markdown-it-py. This ensures that loose lists (items separated by newlines) render with proper spacing, complying with the CommonMark spec, while keeping tight lists compact. Updated regression tests to match the corrected output.

rich/markdown.py

@@ -112,10 +112,14 @@ class Paragraph(TextElement):
 
     @classmethod
     def create(cls, markdown: Markdown, token: Token) -> Paragraph:
-        return cls(justify=markdown.justify or "left")
+        return cls(
+            justify=markdown.justify or "left",
+            visible=not getattr(token, "hidden", False),
+        )
 
-    def __init__(self, justify: JustifyMethod) -> None:
+    def __init__(self, justify: JustifyMethod, visible: bool = True) -> None:
         self.justify = justify
+        self.visible = visible
 
     def __rich_console__(
         self, console: Console, options: ConsoleOptions
@@ -364,6 +368,10 @@ class ListItem(TextElement):
 
     def on_child_close(self, context: MarkdownContext, child: MarkdownElement) -> bool:
         self.elements.append(child)
+        # FIX: If the child is a visible paragraph (loose list), add a blank line
+        if getattr(child, "visible", False):
+            # Text(" ") creates exactly one new line of height
+            self.elements.append(Text(" "))
         return False
 
     def render_bullet(self, console: Console, options: ConsoleOptions) -> RenderResult: