feat: add an index.md for getting-started section, with accurate link…

[codeEvolveZenith345]

Adds a streamlined, navigation-focused index.md to /docs/versioned/getting-started/ for Knative docs. This landing page provides clear orientation with accurate links and meta-navigation to existing tutorials, based on verified documentation structure. The update replaces broken/obsolete links, references current docs, simplifies function resources, and improves user journeys.
Fixes #6314 – ensures readers access the correct guides and resources.

Proposed Changes

• Adds concise index.md navigation hub to getting-started
• Replaces outdated or missing links with verified documentation paths
• Removes duplicate/obsolete files and clarifies user journeys

closes #6314

[knative-prow]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: codeEvolveZenith345
Once this PR has been reviewed and has the lgtm label, please assign houshengbo for approval. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[netlify]

✅ Deploy Preview for knative ready!

Built without sensitive environment variables

Name	Link
🔨 Latest commit	cd3d622
🔍 Latest deploy log	https://app.netlify.com/projects/knative/deploys/6910fa1593e3aa0008d8cdd7
😎 Deploy Preview	https://deploy-preview-6498--knative.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.

[codeEvolveZenith345]

Hi @evankanderson @Cali0707
the failing workflow is unrelated to my changes...

This PR is ready for review.
Thank you.