feat: update navigation with Docs rename and Cloud signup pill

[roomote]

This PR updates the website navigation with the following changes:

• Renamed "Documentation" to "Docs" in both desktop and mobile navigation
• Added a new pill-shaped element after "Careers" with text "Roo Code Cloud is coming · Sign up"
• The "Sign up" text is a clickable link that opens the provided Notion URL in a new tab

The new element uses appropriate styling to match the existing design system and is responsive for both desktop and mobile views.

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Important

Updates nav-bar.tsx to rename "Documentation" to "Docs" and add a new pill-shaped "Sign up" element linking to Notion.

• Navigation Update:
  • Renamed "Documentation" to "Docs" in nav-bar.tsx for both desktop and mobile views.
  • Added a new pill-shaped element after "Careers" with text "Roo Code Cloud is coming · Sign up" in nav-bar.tsx.
  • "Sign up" is a clickable link opening a Notion URL in a new tab.
• Styling:
  • New element styled to match existing design system and is responsive for desktop and mobile.

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[github-actions]

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