fix(theme): use single nav landmark for docs sidebar

[yoshibase]

Summary

Fixes #8429 (landmark structure only)

The docs sidebar currently nests landmarks: an outer <aside> (complementary) wraps an inner <nav aria-label="Docs sidebar">. NVDA announces both before you reach any doc link — "complementary landmark … docs sidebar navigation landmark …".

This PR:

• Replaces the outer <aside> with a plain <div> container (no complementary landmark)
• Moves the single <nav aria-label="Docs sidebar"> to wrap the logo, menu, and collapse button together

Issue #8429 also mentions hiding the duplicate sidebar logo from screen readers when navbar.hideOnScroll is on. I left that out of this PR on purpose — I will open a separate follow-up for it so reviewers can evaluate one concern at a time.

Test plan

Preview: https://deploy-preview-12291--docusaurus-2.netlify.app/docs/introduction (once Netlify build completes)

Compare against main: https://docusaurus.io/docs/introduction

Tools: Chrome, NVDA (Windows) or VoiceOver (macOS), DevTools

1. Inspect the DOM (Chrome DevTools)

1. Open the deploy preview docs page.
2. Right-click the left doc sidebar → Inspect.
3. Walk up the tree from a sidebar menu link.

Expected after this PR:

<div class="...docSidebarContainer...">
  <div class="...sidebarViewport...">
    <nav aria-label="Docs sidebar" class="...sidebar...">
      <!-- logo (if hideOnScroll), menu <ul>, collapse button -->
    </nav>
  </div>
</div>

On main today:

<aside class="...docSidebarContainer...">
  ...
    <div class="...sidebar...">
      <nav aria-label="Docs sidebar"> ... </nav>
    </div>
  ...
</aside>

The point: one navigation landmark for the sidebar, not complementary + navigation.

2. NVDA landmark list

1. Install NVDA: https://www.nvaccess.org/download/
2. Open the preview URL in Chrome with NVDA running.
3. Press NVDA + F7 → Landmarks tab.

Check	Main (docusaurus.io)	This PR preview
Complementary landmark for docs sidebar	Yes (<aside>)	No
Navigation landmark "Docs sidebar"	Yes (nested inside complementary)	Yes (standalone)

3. Keyboard navigation still works

1. Press Tab repeatedly through the sidebar links.
2. All doc links should be reachable in the same order as before.
3. If your site config has a collapsible sidebar, the collapse button should still work.

4. VoiceOver spot check (macOS)

1. Safari → preview URL.
2. VO + U → Landmarks rotor.
3. Confirm there is a Docs sidebar navigation landmark and no extra complementary landmark for the sidebar column.

5. axe DevTools (optional)

Scan the page with axe DevTools. Removing a redundant <aside> should not introduce new violations. Landmark-related informational notices are fine — compare against main rather than expecting zero notices.

What proves the fix

Steps 1–2 show the sidebar is exposed as one navigation landmark instead of complementary + navigation stacked together. That matches the structure requested in #8429.

[netlify]

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[yoshibase]

Follow-up to #12283 (closed — PR head stuck after force-push rewrite).

This PR has the narrowed scope and expanded test plan @slorber requested. Preview link will appear in the Netlify bot comment once the build finishes.

[netlify]

✅ [V2]

Built without sensitive environment variables

Name	Link
🔨 Latest commit	0d92b79
🔍 Latest deploy log	https://app.netlify.com/projects/docusaurus-2/deploys/6a596e8c3309d200087f892b
😎 Deploy Preview	https://deploy-preview-12291--docusaurus-2.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

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[yoshibase]

Ready for review — narrowed to single-nav landmark only. Preview: https://deploy-preview-12291--docusaurus-2.netlify.app/docs/introduction

[yoshibase]

Ready for review — scope narrowed to landmark structure only (logo aria-hidden deferred to a follow-up). Preview: https://deploy-preview-12291--docusaurus-2.netlify.app/docs/introduction

[yoshibase]

@slorber — ready for review when you have time. Narrowed to landmark structure only (#8429). Preview: https://deploy-preview-12291--docusaurus-2.netlify.app/docs/introduction — test plan is in the description (DevTools + NVDA/VoiceOver).