Add RubyLLM::Contract to Ecosystem

[justi]

What this does

This adds the gem RubyLLM::Contract to the Ecosystem documentation. It is a Ruby library that wraps RubyLLM::Chat with input/output contracts, business-rule validation, retry with model escalation on validation failure, pre-flight cost ceilings, and a regression-eval framework. It catches schema-valid-but-logically-wrong output at the boundary of your system before it ships to production.

Example Usage

class SummarizeArticle < RubyLLM::Contract::Step::Base
  prompt <<~PROMPT
    Summarize this article for a UI card. Return a short TL;DR,
    3 to 5 key takeaways, and a tone label.

    {input}
  PROMPT

  output_schema do
    string :tldr
    array  :takeaways, of: :string, min_items: 3, max_items: 5
    string :tone, enum: %w[neutral positive negative analytical]
  end

  validate("TL;DR fits the card")  { |o, _| o[:tldr].length <= 200 }
  validate("takeaways are unique") { |o, _| o[:takeaways] == o[:takeaways].uniq }

  retry_policy models: %w[gpt-4.1-nano gpt-4.1-mini gpt-4.1]
end

result = SummarizeArticle.run(article_text)
result.parsed_output  # => { tldr: "...", takeaways: [...], tone: "analytical" }

The gem is complementary to RubyLLM::Tribunal - Contract gates at runtime (before output reaches your code, with retries on failure), Tribunal grades at test-time (after output is in your code, in a spec).

Type of change

• Documentation

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

API changes

• No API changes

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.10%. Comparing base (f82711f) to head (af2eb09).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

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  Coverage   82.10%   82.10%           
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  Files         137      137           
  Lines        6344     6344           
  Branches     1122     1122           
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  Hits         5209     5209           
  Misses        684      684           
  Partials      451      451           

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