Feature: Show explore extensions dialog when no extensions are installed

[JayadityaGit]

What would you like to be added?

Currently, when users run extension-related commands (/extensions list, /extensions update, /extensions restart) with no extensions installed, they either see empty lists or generic error messages. This doesn't guide users toward discovering and installing extensions, which is a missed opportunity for improving user onboarding and extension adoption.

Proposed Solution

Show a friendly confirmation dialog when users run certain extension commands with no extensions installed, prompting them to explore the extensions gallery.

Affected Commands

• /extensions list - When no extensions are installed
• /extensions update - When no extensions are installed
• /extensions restart --all - When no extensions are installed (only with --all flag)

Dialog Behavior

• Message: "No extensions installed. Would you love to explore extensions?"
• Options: Yes / No
• On Yes: Opens the extensions page in the default browser (https://geminicli.com/extensions/)
• On No: Exits cleanly without additional output

Why is this needed?

1. Better User Onboarding: Guides new users to discover extensions
2. Improved UX: Provides actionable next steps instead of empty states
3. Increased Extension Adoption: Makes it easier for users to discover available extensions
4. Consistent Behavior: Applies uniformly across list, update, and restart commands

Additional context

No response

[JayadityaGit]

/assign

[gemini-cli]

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