Add comprehensive list of free models to .env file for easy user selection

[Copilot]

Enhanced the .env file to include a comprehensive list of free models available on OpenRouter.ai, allowing users to easily select their preferred model by uncommenting the desired option.

Changes Made

Enhanced .env File

• Added 22 free model options, all commented out by default
• Organized models into clear categories (popular models, additional free models)
• Added detailed instructions on how to uncomment and use different models
• Maintained backward compatibility with existing configuration

Updated Documentation

• Updated README.md to reflect the new comprehensive model list
• Added examples showing how to uncomment models
• Clarified that users can browse the full list in their .env file

Features

Before:

# Only basic examples in comments
# Example: OPENROUTER_MODEL=qwen/qwq-32b:free 
# Example: OPENROUTER_MODEL=deepseek/deepseek-r1-0528:free
OPENROUTER_MODEL=

After:

# === FREE MODELS ===
# Uncomment ONE of the following lines to use a specific free model:

# Default model (used when no model is specified)
# OPENROUTER_MODEL=mistralai/mistral-small-3.2-24b-instruct:free

# Popular free models mentioned in documentation
# OPENROUTER_MODEL=qwen/qwq-32b:free
# OPENROUTER_MODEL=deepseek/deepseek-r1-0528:free
# OPENROUTER_MODEL=google/gemini-2.0-flash-exp:free

# Additional free models commonly available on OpenRouter
# OPENROUTER_MODEL=meta-llama/llama-3.1-8b-instruct:free
# OPENROUTER_MODEL=meta-llama/llama-3.1-70b-instruct:free
# ... and 16 more options!

User Experience Improvements

• Easy Model Selection: Users can now browse 22 free models and simply uncomment their preferred choice
• Clear Organization: Models are categorized and well-documented
• Backward Compatible: Existing behavior is preserved (uses default model when none specified)
• No Configuration Errors: Users don't need to remember or type model names manually

Testing

• ✅ Default behavior preserved (uses mistralai/mistral-small-3.2-24b-instruct:free when no model specified)
• ✅ Model selection works correctly when users uncomment a model
• ✅ .env file parsing works correctly with all shell environments
• ✅ Script functionality unchanged
• ✅ All 22 free model options available and properly formatted

Fixes #2.

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[cerebrux]

Excelent work @copilot !