fix(markdown_parser): emit MdIndentTokenList for headers inside list items

crates/biome_markdown_parser/src/syntax/list.rs

@@ -1902,6 +1902,10 @@ fn parse_first_line_atx_heading(p: &mut MarkdownParser, state: &mut ListItemLoop
 
     let header_m = p.start();
 
+    // Emit the required MdIndentTokenList slot (slot 0) so the CST matches the grammar.
+    // In list context we are never at line start, so this produces an empty list node.
+    p.emit_line_indent(MAX_BLOCK_PREFIX_INDENT);
+
     // Can't reuse header::parse_hash_list(): in list context `#` may be lexed as
     // MD_TEXTUAL_LITERAL and requires bump_remap. Keep in sync with parse_hash_list().
     let hash_list_m = p.start();

crates/biome_markdown_parser/tests/md_test_suite/ok/header_in_list.md

@@ -0,0 +1,15 @@
+- # Foo
+- Bar
+  ---
+  baz
+
+- ## Level 2
+
+* ### Level 3
+
+- ###### Level 6
+
+- # Trailing hash #
+
+1. # Ordered heading
+2. ## Ordered level 2