feat(models): add support for Claude 4.5 Sonnet model in registry

- Introduced new model definition for `Claude 4.5 Sonnet` with metadata and creation details.
- Ensures compatibility and access to the latest Claude model variant.

internal/registry/model_definitions.go

@@ -8,6 +8,14 @@ import "time"
 // GetClaudeModels returns the standard Claude model definitions
 func GetClaudeModels() []*ModelInfo {
 	return []*ModelInfo{
+		{
+			ID:          "claude-sonnet-4-5-20250929",
+			Object:      "model",
+			Created:     1759104000, // 2025-09-29
+			OwnedBy:     "anthropic",
+			Type:        "claude",
+			DisplayName: "Claude 4.5 Sonnet",
+		},
 		{
 			ID:          "claude-opus-4-1-20250805",
 			Object:      "model",