This page has no title frontmatter and no # Heading, so Auto Sidebar titles it from its file name, guide-to-the-cli.md.
With titleCase
titleCase is on by default. Articles, short conjunctions and prepositions such as a, the, and, of and to stay lowercase unless they are the first or last word, so the sidebar shows Guide to the Cli.
Without titleCase
With titleCase: false, every word is capitalised: "Guide To The Cli".
Only first letters change case, so "Cli" stays "Cli". Add { cli: 'CLI' } to titleReplacements to write it as "CLI". Titles an author wrote are never re-cased.