feat: implement custom OpenAI-compatible providers with direct API keys

[francojc]

Summary

Implements support for custom OpenAI-compatible providers (GitHub Copilot, Groq, etc.) with direct API key authentication and repo-local configuration.

Key Features

• Dynamic provider registration using YAML configuration
• Support for any OpenAI-compatible API endpoint
• Direct command-line API keys (no environment variables)
• Comprehensive Pydantic validation
• Repo-local providers.yaml configuration
• Backward compatibility with all built-in providers

Configuration Example

custom_providers:
  - name: "github-copilot"
    display_name: "GitHub Copilot"
    api_base_url: "https://api.githubcopilot.com"
    models:
      - name: "gemini-2.5-pro"
        context_length: 1000000
        max_output_tokens: 8192

Usage

# Development
uv run consult7 github-copilot your-api-key --test

# Claude Desktop
"args": ["run", "--directory", "/path/to/project", "consult7", "github-copilot", "API_KEY"]

Test Plan

• Custom provider registration working
• Built-in providers unchanged
• Configuration validation
• API key handling
• Error isolation
• Documentation updated

🤖 Generated with Claude Code