feat: add Gemini CLI extension support

[vchomakov]

Add Gemini CLI Extension Support

Summary

Enables installation of the Redis MCP Server as a Gemini CLI extension with a single command.

What's Added

• gemini-extension.json - Extension configuration for Gemini CLI
• GEMINI.md - A documentation with configuration examples

Usage

# Install the extension
gemini extensions install redis/mcp-redis

# Configure Redis connection (optional)
export REDIS_URL=redis://localhost:6379/0

Technical Details

• Extension version: 0.1.0
• Uses uvx to download redis-mcp-server@latest from PyPI
• Configuration priority: REDIS_URL → individual env vars → defaults

Testing

Successfully installed mcp-redis extension from GitHub:

$ gemini extensions install https://github.com/redis/mcp-redis.git --ref=feat/gemini-cli-extension
Extensions may introduce unexpected behavior.
Ensure you have investigated the extension source and trust the author.
This extension will run the following MCP servers:
  * redis (local): uvx --from redis-mcp-server@latest redis-mcp-server --url ${REDIS_URL}
Do you want to continue? [Y/n]: Y
Extension "mcp-redis" installed successfully and enabled.
$ gemini extensions list
mcp-redis (0.1.0)
 Path: /Users/vasil.chomakov/.gemini/extensions/mcp-redis
 Source: https://github.com/redis/mcp-redis.git (Type: git)
 Ref: feat/gemini-cli-extension
 Context files:
  /Users/vasil.chomakov/.gemini/extensions/mcp-redis/GEMINI.md
 MCP servers:
  redis