Title: Add RubyLLM::Instructor, ::Registry, ::Tokenizer, and ::Turbovec to ecosystem page

[washu]

Description:
Adds four published ecosystem gems to the ecosystem page:

• ruby_llm-instructor — structured, validated outputs with automatic retry (instructor-style, built on RubyLLM::Schema)
• ruby_llm-registry — local-first versioned prompt storage with labels, ERB rendering, diffing, and optional SQLite/AR/Mongo/S3 backends
• ruby_llm-tokenizer — local model-aware token counting and context-window truncation over HF tokenizers / tiktoken / SentencePiece
• ruby_llm-turbovec — embeddable, in-process quantized vector search via a native Rust extension wrapping the turbovec crate

All four are on RubyGems with CI passing and tagged with the ruby-llm topic.

What this does

adds to teh eco system page of available gems

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

Required for new features

• I opened an issue before writing code and received maintainer approval
• Linked issue: #___

PRs for new features or enhancements without a prior approved issue will be closed.

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)

AI-generated code

• I used AI tools to help write this code
• I have reviewed and understand all generated code (required if above is checked)

API changes

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

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.88%. Comparing base (80fe294) to head (38cd65b).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #812   +/-   ##
=======================================
  Coverage   82.88%   82.88%           
=======================================
  Files         142      142           
  Lines        6574     6574           
  Branches     1148     1148           
=======================================
  Hits         5449     5449           
  Misses        663      663           
  Partials      462      462           

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