feat: add expandable diff excerpts with configurable context

src/session.rs

@@ -202,6 +202,7 @@ impl EditorSession {
                 config.clipboard_mode
             ));
         }
+        editor.set_diff_context_options(config.diff_context_lines, config.diff_expand_lines);
         let mut plugins = BTreeMap::new();
         for configured in config.plugins {
             let path = configured.path;