[Bug] Down arrow is not working if suggestion dropdown inside snippet only have one item

Reproducible in vscode.dev or in VS Code Desktop?

• Not reproducible in vscode.dev or VS Code Desktop

Reproducible in the monaco editor playground?

• Not reproducible in the monaco editor playground

Monaco Editor Playground Link

https://microsoft.github.io/monaco-editor/playground.html?source=v0.35.0#XQAAAAJeBQAAAAAAAABBqQkHQ5NjdMjwa-jY7SIQ9S7DNlzs5W-mwj0fe1ZCDRFc9ws9XQE0SJE1jc2VKxhaLFIw9vEWSxW3yscw88CE_XEgGR9Ivd8w3mjpSjZSOKE1xhLc1lhytLzTgHexlZdf13AMmb8eWCqPBcz0ifSqHTfhIHUQQZh3WL4dej8ii7Di1rWv30U56tLLpyEnLGYJN5LChcnzNw6oMDYL4hixkD22ehHpv6594EMs6dJ9P1TYZqJVwAACKjltTzi4D0cADCfK3Io7A_VavD7eK_AwOwZybAyNom2JgPgXBKJrJSQlas-hAE8rHloJ9c1Q8oYCEGTJXhDO5dsK8vMuVdxGPoS1E9rYBmveYEGUTA_BD0jjKRMtBUL4mBtRsNjpdBds59C22m2kWnJy_vNoDo0mPRoiF2I5F-_f4AvyjOf5x3OVk0Cd4y_c9TyLOldsuGAbDyUFujS6UAVf5b0oSr_k7WjOUJZDXj1oRWVYFwLp7M3ryVnGR-TON8vKAKLTQiNn2QT5PFmonEuf5s8KD503xQU4d_aIIbeYBGGg1q2M0iHP6sBFtZrPAS6us2B_MYutA_v-Wo-nKSdJRx96jOzSq8r2k1-EYN1UujXB7QZQEeP8YJrwRlHyeifZcTSTuRSxNtsS00FypOGLikPdCzTyzdyJJrLOoHVxnwijxuoN9G6DO96son9PoB_KqFTzJ-Q7t09uKHQb7dbA9zWrGiv_FXfHAA

Monaco Editor Playground Code

function createSuggestions (range) {
  const kind = monaco.languages.CompletionItemKind.Snippet;
  const insertTextRules = monaco.languages.CompletionItemInsertTextRule.InsertAsSnippet;

  return [
    {
      label: 'line',
      kind,
      detail: 'Line',
      insertText: 'Line 1: $1\nLine2: $2\n',
      insertTextRules,
      range,
    },
    {
      label: 'while-do',
      kind,
      detail: 'Inline note',
      insertText: 'note: \'${1:}\'',
      insertTextRules,
      range,
    },
    {
      label: 'for-each',
      kind,
      detail: 'For each loop',
      insertText: 'Some snippet text',
      insertTextRules,
      range,
    },
    {
      label: 'for-in',
      kind,
      detail: 'For in loop',
      insertText: 'Some snippet text',
      insertTextRules,
      range,
    },
  ];
}

monaco.languages.registerCompletionItemProvider("json", {
	provideCompletionItems: function (model, position) {

		var word = model.getWordUntilPosition(position);
		var range = {
			startLineNumber: position.lineNumber,
			endLineNumber: position.lineNumber,
			startColumn: word.startColumn,
			endColumn: word.endColumn,
		};
		return {
			suggestions: createSuggestions(range),
		};
	},
});

monaco.editor.create(document.getElementById("container"), {
	value: '',
	language: "json",
});

Reproduction Steps

1. Type li
2. Press Tab
3. Type wh
4. Press Down arrow
   
5. The cursor goes to the next line
   

Actual (Problematic) Behavior

When the suggestion dropdown inside a snippet's tabstop only has 1 item, pressing Down arrow will go to next line instead of selecting that item

Expected Behavior

Press Down arrow should select the suggestion item when it has only 1 item.

Additional Context

If the suggestion dropdown has more than 1 item, it can be selected using Up/Down arrow. For example:

1. Type li
2. Press Tab
3. Type fo
4. Press Down arrow

Result:

Start with the linked Monaco Editor Playground and the provided TypeScript completion-provider snippet; reproduce the issue by entering the single-item suggestion inside a snippet tabstop and pressing Down. Trace the completion and snippet interaction, then verify that Down selects the sole suggestion instead of moving to the next line, including the contrasting multi-item case.