Remove all duplicate class definitions from coderai

Removed ~2050 lines of duplicate code:
- Pydantic models (ToolFunction, Tool, ChatMessage, etc.) - now from codai.pydantic
- ModelParserAdapter, ToolCallParser - now from codai.models
- NvidiaBackend, VulkanBackend - now from codai.backends
- All other duplicates removed

Now coderai properly imports all classes from codai modules.

codai/models/__init__.py

@@ -13,6 +13,8 @@ from .parser import (
     PhiParser,
     ApexBig50Parser,
     OpenAIFormatter,
+    ToolCallParser,
+    ModelParserAdapter,
 )
 
 from .templates import AgenticTemplateManager
@@ -31,5 +33,7 @@ __all__ = [
     'PhiParser',
     'ApexBig50Parser',
     'OpenAIFormatter',
+    'ToolCallParser',
+    'ModelParserAdapter',
     'AgenticTemplateManager',
 ]