Adding RubyLLM::RedCandle to the ecosystem page (documentation only)

[cpetersen]

What this does

This PR adds scientist-labs/ruby_llm-red_candle to the ecosystem page.

The ruby_llm-red_candle gem adds a red_candle provider to RubyLLM. Red candle allows the user to run models locally, directly in the ruby process using the candle rust crate from HuggingFace.

We had originally added red-candle to the base gem in #404. I can understand the reluctance to merge that PR, it's a big dependency. We've now moved it to it's own gem that can be included by the end user, similar to ruby_llm-mcp or ruby_llm-schema.

Type of change

• Bug fix
• New feature
• Breaking change
• Documentation
• Performance improvement

Scope check

• I read the Contributing Guide
• This aligns with RubyLLM's focus on LLM communication
• This isn't application-specific logic that belongs in user code
• This benefits most users, not just my specific use case

Quality check

• I ran overcommit --install and all hooks pass
• I tested my changes thoroughly
  • For provider changes: Re-recorded VCR cassettes with bundle exec rake vcr:record[provider_name]
  • All tests pass: bundle exec rspec
• I updated documentation if needed
• I didn't modify auto-generated files manually (models.json, aliases.json)

API changes

• Breaking change
• New public methods/classes
• Changed method signatures
• No API changes

Related issues

Fixes #394