Navie doesn't know the location of code selection items

As we can see from the following type, a user code selection doesn't appear to include the file path / location.

  export type CodeSelectionItem = {
    type: 'code-selection';
    content: string;
  };

This is going to hamper the ability of FileChangeExtractorService to perform listFiles, because the file name of code selection items will not be available.

  export function renderItems(items: ContextItem[], includeContent: boolean = true) {
    const renderItem = (i: UserContext.ContextItem) => {
      if (UserContext.isCodeSelectionItem(i) && includeContent) {
        return `<code-selection>\n${i.content}\n</code-selection>`;
      } else if (UserContext.isCodeSnippetItem(i)) {
        const content = includeContent ? `\n<content>${i.content}</content>\n'` : '';
        return `<pinned-snippet>
  <location>${i.location}</location>${content}
</pinned-snippet>`;
      } else if (UserContext.isFileItem(i)) {
        return `<pinned-file><location>${i.location}</location></pinned-file>`;
      }
    };

Start with the CodeSelectionItem type and renderItems function shown in the issue, then trace how code selections reach FileChangeExtractorService. Determine where the file location is lost and verify that listFiles can use it once preserved; the issue is done when code-selection items carry their location through this flow.