fix: skip SGLang FastAPI tests when fastapi not installed (CI fix)

SGLang app tests require fastapi which is an optional dependency.
Skip these tests gracefully on CI environments without fastapi installed.

tests/test_sglang_serve.py

@@ -5,6 +5,15 @@ from unittest.mock import patch as mock_patch
 
 import pytest
 
+
+def _has_fastapi():
+    try:
+        import fastapi  # noqa: F401
+        return True
+    except ImportError:
+        return False
+
+
 # ─── SGLang Detection Tests ──────────────────────────────────────────────
 
 
@@ -112,32 +121,17 @@ class TestSGLangRuntimeCreation:
 # ─── SGLang FastAPI App Tests ────────────────────────────────────────────
 
 
+@pytest.mark.skipif(
+    not _has_fastapi(),
+    reason="fastapi not installed",
+)
 class TestSGLangApp:
-    """Test SGLang FastAPI app creation."""
+    """Test SGLang FastAPI app creation (requires fastapi)."""
 
     def test_create_sglang_app_returns_fastapi(self):
         """create_sglang_app should return a FastAPI application."""
         mock_runtime = MagicMock()
 
-        with mock_patch("fastapi.FastAPI") as mock_fastapi:
-            mock_app = MagicMock()
-            mock_fastapi.return_value = mock_app
-
-            from soup_cli.utils.sglang import create_sglang_app
-
-            app = create_sglang_app(
-                runtime=mock_runtime,
-                runtime_model_name="test-model",
-                model_name="test",
-            )
-
-        assert app is not None
-
-    def test_sglang_app_has_health_endpoint(self):
-        """SGLang app should have /health endpoint."""
-        mock_runtime = MagicMock()
-        mock_runtime.generate.return_value = {"text": "test", "meta_info": {}}
-
         from soup_cli.utils.sglang import create_sglang_app
 
         app = create_sglang_app(
@@ -146,7 +140,20 @@ class TestSGLangApp:
             model_name="test",
         )
 
-        # Check that routes include /health
+        assert app is not None
+
+    def test_sglang_app_has_health_endpoint(self):
+        """SGLang app should have /health endpoint."""
+        mock_runtime = MagicMock()
+
+        from soup_cli.utils.sglang import create_sglang_app
+
+        app = create_sglang_app(
+            runtime=mock_runtime,
+            runtime_model_name="test-model",
+            model_name="test",
+        )
+
         routes = [route.path for route in app.routes]
         assert "/health" in routes
 
@@ -218,8 +225,9 @@ class TestServeSGLangCommand:
             ])
         assert result.exit_code != 0
 
+    @pytest.mark.skipif(not _has_fastapi(), reason="fastapi not installed")
     def test_serve_unknown_backend_shows_error(self, tmp_path):
-        """serve --backend invalid should show error."""
+        """serve --backend invalid should show error listing valid backends."""
         from typer.testing import CliRunner
 
         from soup_cli.cli import app