Refactor AI Agent and AI Config handling across multiple files

- Updated function signatures to accept AI Agent and AI Config as non-pointer types for better clarity and safety.
- Modified instances where AI Agent and AI Config were dereferenced to improve code readability.
- Removed unnecessary nil checks for AI Agent and AI Config, simplifying the logic.
- Adjusted related tests and services to align with the new function signatures.
- Cleaned up code in runtime, skills, and executor packages to ensure consistency in handling AI configurations.

internal/ai/openai_client.go

@@ -13,7 +13,7 @@ import (
 	"cs-agent/internal/repositories"
 )
 
-func newOpenAIClient(config *models.AIConfig) openai.Client {
+func newOpenAIClient(config models.AIConfig) openai.Client {
 	opts := []option.RequestOption{
 		option.WithAPIKey(config.APIKey),
 		option.WithBaseURL(config.BaseURL),