feat: list-indent folding — gutter chevrons on nested list/task items, same click/shift/ctrl/ctrl-shift gestures as headings, plus caret snap out of list-marker prefix

Author: wilfreddenton

src/buffer.rs

@@ -12,8 +12,8 @@ static NEXT_VERSION: AtomicU64 = AtomicU64::new(1);
 use crate::highlight::{HighlightSpan, Highlighter};
 use crate::inline::{StyledRegion, extract_all_inline_styles, styles_in_range};
 use crate::marker::{
-    HeadingInfo, LineMarkers, ParsedNodes, collect_node_infos, is_line_in_checked_task,
-    is_line_in_code_block, markers_at_from_infos,
+    HeadingInfo, LineMarkers, ListItemInfo, ParsedNodes, collect_node_infos,
+    is_line_in_checked_task, is_line_in_code_block, markers_at_from_infos,
 };
 use crate::parser::{MarkdownParser, MarkdownTree};
 use crate::table::{RowKind, TableInfo};
@@ -674,6 +674,12 @@ impl BufferContent {
         &self.parsed().headings
     }
 
+    /// List items in document order (parent before child), for list folding.
+    /// Rc-cached with the parse tree, so auto-invalidated on edit.
+    pub fn list_items(&self) -> &[ListItemInfo] {
+        &self.parsed().list_items
+    }
+
     /// Compute LineMarkers for a specific line on demand.
     pub fn line_markers(&self, line_idx: usize) -> LineMarkers {
         line_markers_from(&self.parsed, &self.text, line_idx)