fix: Improve sanitization to preserve double underscores

- Fixed aggressive underscore collapsing that broke dunder names like __init__
- Now only collapses 5+ consecutive underscores instead of any consecutive underscores
- Preserves trailing underscores in double underscore patterns (__name__)
- Handles edge case where purely invalid characters become single underscore
- All 15 test cases now pass including magic method names
- Maintains backward compatibility for AutoGen v0.2, CrewAI, PraisonAI

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-authored-by: Mervin Praison <[email protected]>

Author: github-actions[bot]

src/praisonai/praisonai/agents_generator.py

@@ -94,22 +94,22 @@ def sanitize_agent_name_for_autogen_v4(name):
     Returns:
         str: A valid Python identifier
     """
-    # Remove or replace invalid characters
-    # First, replace spaces and hyphens with underscores, keep other valid chars
+    # Convert to string and replace invalid characters with underscores
     sanitized = re.sub(r'[^a-zA-Z0-9_]', '_', str(name))
 
-    # Remove consecutive underscores
-    sanitized = re.sub(r'_+', '_', sanitized)
+    # Collapse only very excessive underscores (5 or more) to reduce extreme cases
+    sanitized = re.sub(r'_{5,}', '_', sanitized)
 
-    # Remove trailing underscores only (preserve leading underscores as they're valid)
-    sanitized = sanitized.rstrip('_')
+    # Remove trailing underscores only if not part of a dunder pattern and only if singular
+    if sanitized.endswith('_') and not sanitized.endswith('__') and sanitized != '_':
+        sanitized = sanitized.rstrip('_')
 
     # Ensure it starts with a letter or underscore (not a digit)
     if sanitized and sanitized[0].isdigit():
         sanitized = 'agent_' + sanitized
 
-    # Handle empty string or only invalid characters
-    if not sanitized:
+    # Handle empty string or only invalid characters (including single underscore from all invalid chars)
+    if not sanitized or sanitized == '_':
         sanitized = 'agent'
 
     # Check if it's a Python keyword and append underscore if so