[Feature] gitagent test -- run against example scenarios

[shreyas-lyzr]

Summary

Add a gitagent test command that runs an agent against predefined test scenarios.

Problem

There is no standard way to verify that an agent behaves correctly before deploying it. Agent developers need a testing framework analogous to unit tests for code.

Proposed Solution

# Run all tests for the current agent
gitagent test

# Run a specific test scenario
gitagent test --scenario greeting

# Run with a specific adapter
gitagent test --adapter openai

Test scenarios would live in tests/ or examples/ within the agent repo:

# tests/greeting.yaml
name: greeting-test
input: "Hello, who are you?"
expect:
  contains: ["agent name"]
  tone: professional
  max_tokens: 500

Acceptance Criteria

• gitagent test command implemented
• YAML-based test scenario format defined
• Works with multiple adapters
• Clear pass/fail output
• Documentation added