docs: refresh landing terminal demo and apply NVIDIA fern theme

[aschilling-nv]

Summary

Refresh the docs landing page so the terminal demo no longer depends on globally-loaded CSS, switch the Fern instance to the NVIDIA theme, and bump the Fern CLI to a current version.

Related Issue

N/A

Changes

• Extract the landing-page terminal demo into a reusable <CommandTerminal /> component with inline styles, dropping the dependency on nc-* CSS classes previously sourced from fern/main.css.
• Animate a second command line cycling through claude / opencode / codex using @keyframes scoped inside the component.
• Inline the BadgeLinks layout styles so the component renders correctly without .badge-links from global CSS.
• Add docs/_components/jsx.d.ts so editors stop flagging the React global in component TSX files.
• Switch the Fern instance to global-theme: nvidia with multi-source: true.
• Bump Fern CLI to 5.40.0 and drop the no-longer-needed basepath-aware experimental flag.
• Register fern/components/ as a second mdx-components directory.
• Remove the unused Adobe analytics <script> tag.

Testing

• mise run license:check passes
• mise run markdown:lint:md passes
• mise run pre-commit — test:rust fails locally due to a missing system z3.h header (pre-existing environment issue, no Rust code changed in this PR). Other relevant lint subsets pass.
• Fern preview verified visually — please confirm via the docs-preview workflow that the terminal animation and badge layout render as intended.

Checklist

• Follows Conventional Commits
• Commits are signed off (DCO)

[github-actions]

All contributors have signed the DCO ✍️ ✅
_{Posted by the DCO Assistant Lite bot.}

[aschilling-nv]

@miyoungc - This should be good to go. However, please build this locally to ensure it meets your standards.

[miyoungc]

preview: https://nvidia-preview-98ed077c-20c4-4eff-ab75-5d9e9079279a.docs.buildwithfern.com/openshell/home

[pimlock]

@aschilling-nv Thank you, this looks good!

One thing I noticed is that License link in the navigation is being partially cut out:

I think I remember fixing that in the CSS in the current version by adding some padding.

[aschilling-nv]

@aschilling-nv Thank you, this looks good!

One thing I noticed is that License link in the navigation is being partially cut out:

I think I remember fixing that in the CSS in the current version by adding some padding.

This issue has been corrected in the global theme and is viewable here: https://nvidia-preview-ddd91916-5bb0-4c85-bed4-316e3cfdb458.docs.buildwithfern.com/openshell/resources/license