docs: Enhance CLI documentation with new authentication, browser, and…

[masnwilliams]

TL;DR

Organized and expanded the CLI documentation, adding new, dedicated pages for auth, apps, and browsers commands.

Why we made these changes

To improve the clarity, organization, and completeness of the CLI reference documentation. Splitting the docs into logical sections makes it easier for users to find information on specific commands and their various flags.

What changed?

• Refactored reference/cli.mdx: Converted the main CLI doc into a high-level overview and quick start guide, replacing detailed command tables with cards linking to the new, specific pages.
• Added reference/cli/auth.mdx: New documentation for authentication commands like kernel login, logout, and auth status.
• Added reference/cli/apps.mdx: New documentation for app management commands, including deploy, invoke, list, and logs.
• Added reference/cli/browsers.mdx: New, comprehensive documentation for managing remote browsers and their filesystems.
• Updated docs.json: Added the new pages to the CLI section of the site navigation.

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