feat(api, xai): add xAI Grok video model support with API integration

- Introduced new xAI `grok-imagine-video` model for video generation with configurable options (e.g., duration, size, resolution).
- Implemented video-specific API endpoints (`/v1/videos`, `/v1/videos/generations`, `/v1/videos/edits`, `/v1/videos/extensions`), including request validation and model handling.
- Enhanced model registry with `xaiBuiltinVideoModelID` and metadata for video capabilities.
- Added unit tests to validate video model support, request structures, and API response handling.
- Extended `XAIExecutor` to integrate video generation and retrieval via runtime requests.

internal/logging/gin_logger.go

@@ -21,6 +21,7 @@ var aiAPIPrefixes = []string{
 	"/v1/chat/completions",
 	"/v1/completions",
 	"/v1/images",
+	"/v1/videos",
 	"/v1/messages",
 	"/v1/responses",
 	"/v1beta/models/",

internal/logging/gin_logger_test.go

@@ -66,4 +66,10 @@ func TestIsAIAPIPathIncludesImages(t *testing.T) {
 	if !isAIAPIPath("/v1/images/edits") {
 		t.Fatalf("expected /v1/images/edits to be treated as AI API path")
 	}
+	if !isAIAPIPath("/v1/videos") {
+		t.Fatalf("expected /v1/videos to be treated as AI API path")
+	}
+	if !isAIAPIPath("/v1/videos/video_123") {
+		t.Fatalf("expected /v1/videos/video_123 to be treated as AI API path")
+	}
 }