Remove idx from docs navigation

[shaneauerbach]

Remove the "Sim IDX" navigation tab from docs.json.

This change prevents new users from naturally discovering IDX through the documentation navigation, aligning with the "Kill IDX" project's goal, while ensuring existing IDX documentation remains accessible via direct URLs.

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Linear Issue: IDX-1190

 

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Note

Removes the "Sim IDX" tab and all its groups from docs.json navigation.

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[cursor]

Cursor Agent can help with this pull request. Just @cursor in comments and I'll start working on changes in this branch.
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