This PR migrates the OpenShell docs to Fern and carries the follow-up cleanup needed to make the migrated site usable and close to the existing docs experience. It focuses on navigation, content structure, code block behavior, and landing-page polish, while leaving CI workflow work out of this PR.
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Signed-off-by: Lawrence Lane <llane@nvidia.com>
Co-authored-by: Piotr Mlocek <pmlocek@nvidia.com>