Title hidden in sidebar when disabled in navbar

I have:

• searched the issue tracker for similar issues
• installed the latest version of Quarto CLI
• formatted my issue following the Bug Reports guide

Bug description

If you add a navbar to a Quarto website (I've personally only tested this on a "book" website), it removes the title from the sidebar above the TOC. Instead, the title is shown up in the navbar by default. No problem. However, if I hide it from the navbar, it should show back up in the sidebar.

Also, adding "title: true" or "title: "My Book Title"" under the sidebar config in _quarto.yml doesn't restore the title.

However, the div and a href are still in the sidebar, and so the place for the title still takes up vertical space, but it just doesn't contain the text it should. Here is the html that is still included in the sidebar:

<div class="pt-lg-2 mt-2 text-left sidebar-header sidebar-header-stacked">
      <a href="http://localhost:3092/" class="sidebar-logo-link" data-original-href="http://localhost:3092/index.html">
      </a>
      </div>

I believe this is the same bug reported without enough detail here: https://github.com/quarto-dev/quarto-cli/issues/8661

Attached is a minimal _quarto.yml file that demonstrates what I mean.

Steps to reproduce

Add a navbar to a quarto book, hiding the title in it, like so:

project:
  type: book

book:
  title: "test quarto book 2025"
  author: "Norah Jones"
  date: "9/18/2025"
  chapters:
    - index.qmd
  sidebar:
    search: true
  navbar: 
    title: false
    search: false
    left:
      - text: Test
        href: http://test.com
      - text: Example
        href: https://example.com

format:
  html:
    theme:
      - cosmo
      - brand

Actual behavior

Title disappears from sidebar also.

Expected behavior

Title should only be removed from the navbar and should be visible in the sidebar.

Your environment

Mac OS 26

Quarto check output

Quarto 1.8.24
[✓] Checking environment information...
Quarto cache location: /Users/jtbayly/Library/Caches/quarto
[✓] Checking versions of quarto binary dependencies...
Pandoc version 3.6.3: OK
Dart Sass version 1.87.0: OK
Deno version 2.3.1: OK
Typst version 0.13.0: OK
[✓] Checking versions of quarto dependencies......OK
[✓] Checking Quarto installation......OK
Version: 1.8.24
Path: /Applications/quarto/bin

[✓] Checking tools....................OK
TinyTeX: (not installed)
Chromium: (not installed)

[✓] Checking LaTeX....................OK
Using: Installation From Path
Path: /Library/TeX/texbin
Version: 2020

[✓] Checking Chrome Headless....................OK
Using: Chrome found on system
Path: /Applications/Google Chrome.app/Contents/MacOS/Google Chrome
Source: MacOS known location

[✓] Checking basic markdown render....OK

[✓] Checking Python 3 installation....OK
Version: 3.13.5
Path: /usr/local/opt/python@3.13/bin/python3.13
Jupyter: (None)

  Jupyter is not available in this Python installation.
  Install with python3 -m pip install jupyter

[✓] Checking R installation...........OK
Version: 4.3.0
Path: /Library/Frameworks/R.framework/Resources
LibPaths:
- /Library/Frameworks/R.framework/Versions/4.3-arm64/Resources/library
knitr: 1.43
rmarkdown: 2.24

[✓] Checking Knitr engine render......OK

Start by reproducing the issue with the minimal _quarto.yml configuration in the report, using a Quarto book with navbar title disabled. Inspect the generated sidebar HTML and confirm that the title is visible in the sidebar while remaining hidden from the navbar; an open pull request is already linked to this issue.