Add RubyLLM::Tribunal to ecosystem page

docs/_reference/ecosystem.md

@@ -246,6 +246,42 @@ For detailed documentation, setup instructions, and examples, visit the [OpenTel
 
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+## RubyLLM::Tribunal
+
+**LLM Evaluation and Testing for Ruby**
+
+[`RubyLLM::Tribunal`](https://github.com/Alqemist-labs/ruby_llm-tribunal) helps you evaluate and test LLM outputs in Ruby applications. It combines deterministic assertions for fast checks with model-based evaluations for quality, faithfulness, and safety.
+
+### Why Use RubyLLM::Tribunal?
+
+When building LLM features, you often need to verify that responses are:
+
+- Grounded in retrieved context
+- Relevant to the user's request
+- Free from hallucinations or unsafe content
+- Resistant to jailbreak or prompt injection attempts
+
+`RubyLLM::Tribunal` brings these checks into your RSpec or Minitest suite.
+
+### Key Features
+
+- Deterministic assertions for exact matches, regexes, JSON validation, and other fast checks
+- LLM-as-judge assertions for faithfulness, relevance, correctness, and refusal behavior
+- Assertions for hallucinations, toxicity, harmful content, bias, jailbreaks, and PII exposure
+- Red team attacks to generate adversarial prompts and test defenses
+- Multiple reporters including Console, JSON, HTML, JUnit, and GitHub Actions
+- Test helpers for RSpec and Minitest
+
+### Installation
+
+```bash
+gem install ruby_llm-tribunal
+```
+
+For detailed documentation and examples, visit the [RubyLLM::Tribunal repository](https://github.com/Alqemist-labs/ruby_llm-tribunal).
+
+---
+
 ## Community Projects
 
 The RubyLLM ecosystem is growing! If you've built a library or tool that extends RubyLLM, we'd love to hear about it. Consider: