cli editor and pager: Add a comment

Follows up on 13c93d5.

The information I added is explained in that commit's description, but
I feel like it could reduce confusion for future readers of the code.

cli/src/cli_util.rs

@@ -2296,6 +2296,7 @@ pub fn run_ui_editor(settings: &UserSettings, edit_path: &PathBuf) -> Result<(),
         .map_err(|err| CommandError::ConfigError(format!("ui.editor: {err}")))?;
     let exit_status = editor.to_command().arg(edit_path).status().map_err(|err| {
         user_error(format!(
+            // The executable couldn't be found or run; command-line arguments are not relevant
             "Failed to run editor '{name}': {err}",
             name = editor.split_name(),
         ))

cli/src/ui.rs

@@ -218,10 +218,11 @@ impl Ui {
         match self.output {
             UiOutput::Terminal { .. } if io::stdout().is_terminal() => {
                 match UiOutput::new_paged(&self.pager_cmd) {
-                    Ok(new_output) => {
-                        self.output = new_output;
+                    Ok(pager_output) => {
+                        self.output = pager_output;
                     }
                     Err(e) => {
+                        // The pager executable couldn't be found or couldn't be run
                         writeln!(
                             self.warning(),
                             "Failed to spawn pager '{name}': {e}",