Add documentation context to Intro to Terraform docs

[BrianMMcClain]

What

Add documentation context in the left-nav of the Intro to Terraform section of the docs.

Why

Investigation shows users often visit the Intro to Terraform documentation from the main Terraform landing page, but rarely make it out to the documentation unless linked in the individual page. This change adds the similar docs sections to the left-nav in the Intro to Terraform docs to help users find docs easier.

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Merge Checklist

If items do not apply to your changes, add (N/A) and mark them as complete.

Pull Request

• Description links to related pull requests or issues, if any.

Content

• You added redirects to content/terraform-docs-common/redirects.jsonc for moved, renamed, or deleted pages across all affected versions. Refer to Redirects for examples and guidance.
• Links to related content where appropriate (e.g., CLI, language, API endpoints, permissions, etc.).
• Pages with related content are updated and link to this content when appropriate.
• Sidebar navigation files have been updated for added, deleted, reordered, or renamed pages.
• New pages have metadata (page name and description) at the top.
• New images are 2048 px wide. They have HashiCorp standard annotation color (#F92672) and format (rectangle with rounded corners), blurred sensitive details (e.g. credentials, usernames, user icons), and descriptive alt text in the markdown for accessibility.
• New code blocks have the correct syntax and line breaks to eliminate horizontal scroll bars.
• UI elements (button names, page names, etc.) are bolded.
• The Vercel website preview successfully deployed.

Reviews

• I or someone else reviewed the content for technical accuracy.
• I or someone else reviewed the content for typos, punctuation, spelling, and grammar.

[github-actions]

Vercel Previews Deployed

Name	Status	Preview	Updated (UTC)
Dev Portal	✅ Ready (Inspect)	Visit Preview	Thu Dec 4 19:40:06 UTC 2025
Unified Docs API	✅ Ready (Inspect)	Visit Preview	Thu Dec 4 19:35:15 UTC 2025

[github-actions]

Broken Link Checker

No broken links found! 🎉

[rkoron007]

Looks good to me! Left a comment that you'll need to add the "Phases" articles to the versions missing them, but besides that this should be good to go!