documents: a caret inside CRLF reads as its line's end

The code editor splits lines on LF only, so End and Right can leave the
caret between CR and LF. line_start and line_end now read that spot as
the end of its line, so insert_table keeps CRLF around a new table.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/documents/document/block.rs

@@ -251,11 +251,19 @@ fn path<'a>(text: &str, root: &'a Node, at: usize) -> Vec<&'a Node> {
     path
 }
 
+/// `at`, before the CR when it splits a CRLF.
+fn settled(text: &str, at: usize) -> usize {
+    let split = text[..at].ends_with('\r') && text[at..].starts_with('\n');
+    if split { at - 1 } else { at }
+}
+
 pub(super) fn line_start(text: &str, at: usize) -> usize {
+    let at = settled(text, at);
     text[..at].rfind(['\n', '\r']).map_or(0, |at| at + 1)
 }
 
 pub(super) fn line_end(text: &str, at: usize) -> usize {
+    let at = settled(text, at);
     at + text[at..].find(['\n', '\r']).unwrap_or(text.len() - at)
 }
 

src/documents/document/tests/tools.rs

@@ -69,6 +69,24 @@ fn a_new_table_goes_after_the_caret_line(cx: &mut TestAppContext) {
     );
 }
 
+#[gpui::test]
+fn a_new_table_after_end_keeps_crlf(cx: &mut TestAppContext) {
+    let (document, cx) = open("Intro\r\nNext\r\n", MarkdownMode::Source, cx);
+    let editor = document.read_with(cx, |document, _| document.editor().clone());
+    let focus = editor.read_with(cx, gpui::Focusable::focus_handle);
+    cx.update(|window, cx| window.focus(&focus, cx));
+    cx.simulate_keystrokes("end");
+    let caret = editor.read_with(cx, |editor, _| editor.primary().range().start);
+    assert_eq!(caret, 6, "End lands between CR and LF");
+    document.update(cx, |document, cx| {
+        document.insert_table(cx).expect("inserted")
+    });
+    assert_eq!(
+        text(&document, cx),
+        "Intro\r\n\r\n|      |      |      |\r\n| ---- | ---- | ---- |\r\n|      |      |      |\r\n|      |      |      |\r\n\r\nNext\r\n"
+    );
+}
+
 #[gpui::test]
 fn a_match_in_visual_opens_its_block_selected(cx: &mut TestAppContext) {
     let (document, cx) = open("# A\n\nfind me here\n", MarkdownMode::Visual, cx);