editor: Represent scroll offset with more precision (#39367)

Closes #5355

Release Notes:

- Fixed rendering glitches with files with more than 16 million lines
(that occured due to floating number rounding errors).

---------

Co-authored-by: Smit Barmase <heysmitbarmase@gmail.com>

crates/agent_ui/src/text_thread_editor.rs

@@ -17,6 +17,7 @@ use editor::{
         BlockPlacement, BlockProperties, BlockStyle, Crease, CreaseMetadata, CustomBlockId, FoldId,
         RenderBlock, ToDisplayPoint,
     },
+    scroll::ScrollOffset,
 };
 use editor::{FoldPlaceholder, display_map::CreaseId};
 use fs::Fs;
@@ -108,7 +109,7 @@ pub enum InsertDraggedFiles {
 
 #[derive(Copy, Clone, Debug, PartialEq)]
 struct ScrollPosition {
-    offset_before_cursor: gpui::Point<f32>,
+    offset_before_cursor: gpui::Point<ScrollOffset>,
     cursor: Anchor,
 }
 
@@ -631,7 +632,7 @@ impl TextThreadEditor {
                         let snapshot = editor.snapshot(window, cx);
                         let cursor_point = scroll_position.cursor.to_display_point(&snapshot);
                         let scroll_top =
-                            cursor_point.row().as_f32() - scroll_position.offset_before_cursor.y;
+                            cursor_point.row().as_f64() - scroll_position.offset_before_cursor.y;
                         editor.set_scroll_position(
                             point(scroll_position.offset_before_cursor.x, scroll_top),
                             window,
@@ -979,7 +980,7 @@ impl TextThreadEditor {
             let cursor_row = cursor
                 .to_display_point(&snapshot.display_snapshot)
                 .row()
-                .as_f32();
+                .as_f64();
             let scroll_position = editor
                 .scroll_manager
                 .anchor()