Fix: Resolve Content Safety Model Resolution Issue

[jeffreyscarpenter]

🐛 Problem Description

The content safety actions were failing with the following error:

WARNING: Error while execution 'content_safety_check_input' with parameters '{...}': 
Could not find prompt for task content_safety_check_input $model=content_safety and model nimchat/nvidia/llama-3_3-nemotron-super-49b-v1_5

🔍 Root Cause Analysis

The issue occurred in the get_task_model function in nemoguardrails/llm/prompts.py. When content safety actions were called with task names like content_safety_check_input $model=content_safety, the system was:

1. Incorrectly using the main model (nvidia/llama-3_3-nemotron-super-49b-v1_5) instead of the specified content safety model
2. Failing to parse the $model=content_safety part of the task name
3. Defaulting to the main model for prompt resolution, causing the lookup to fail

🛠️ Solution

Updated the get_task_model function to properly handle task names with model specifications:

• Added parsing for task names containing $model= specifications
• Extracts model type from task names (e.g., content_safety from content_safety_check_input $model=content_safety)
• Prioritizes specified models over default fallbacks

✅ Changes Made

1. Enhanced Model Resolution Logic - Added parsing for $model= specifications
2. Comprehensive Test Coverage - Added new test case with positive and negative scenarios
3. Backward Compatibility - No breaking changes to existing functionality

🧪 Testing

• ✅ All existing tests continue to pass
• ✅ New test case validates the fix works correctly
• ✅ Content safety actions now work as expected
• ✅ Error messages no longer appear

🔧 Configuration Example

This fix enables proper functioning of configurations like:

models:
  - type: content_safety
    engine: nim
    model: nvidia/llama-3.1-nemoguard-8b-content-safety

rails:
  input:
    flows:
      - content safety check input $model=content_safety

🚀 Impact

Before: Content safety actions failed with confusing error messages
After: Content safety actions work as expected with proper model resolution

This is a non-breaking bug fix that improves the user experience for content safety workflows.