Add tests for 4CM routing endpoints (GET/POST /api/routing)

- TestAPIRouting: 7 tests covering get/set routing mode and breakpoint
- mock_pipeline now has a real set_routing side_effect that updates properties
- Covers connected/disconnected states, mode toggle, breakpoint change, both

tests/test_web.py

@@ -44,6 +44,11 @@ def mock_pipeline():
     pl._master_volume = 0.8
     pl.routing_mode = "mono"
     pl.routing_breakpoint = 7
+
+    def _set_routing(mode, breakpoint=7):
+        pl.routing_mode = mode
+        pl.routing_breakpoint = breakpoint
+    pl.set_routing = MagicMock(side_effect=_set_routing)
     return pl
 
 
@@ -375,4 +380,62 @@ class TestErrors:
 
     def test_empty_model_load_path(self, client):
         res = client.post("/api/models/load", json={"path": ""})
-        assert res.status_code == 400
+        assert res.status_code == 400
+
+
+class TestAPIRouting:
+    """4CM routing mode and breakpoint endpoints."""
+
+    def test_get_routing_default(self, client, mock_pipeline):
+        """GET /api/routing returns current routing config."""
+        res = client.get("/api/routing")
+        assert res.status_code == 200
+        data = res.json()
+        assert data["routing_mode"] == "mono"
+        assert data["routing_breakpoint"] == 7
+
+    def test_get_routing_no_deps(self, client_no_deps):
+        """GET /api/routing returns 503 when pipeline not connected."""
+        res = client_no_deps.get("/api/routing")
+        assert res.status_code == 503
+
+    def test_set_routing_mode_4cm(self, client, mock_pipeline):
+        """POST /api/routing switches to 4CM mode."""
+        res = client.post("/api/routing", json={"routing_mode": "4cm"})
+        assert res.status_code == 200
+        data = res.json()
+        assert data["routing_mode"] == "4cm"
+        mock_pipeline.set_routing.assert_called_with("4cm", 7)
+
+    def test_set_routing_mode_mono(self, client, mock_pipeline):
+        """POST /api/routing switches back to mono."""
+        res = client.post("/api/routing", json={"routing_mode": "mono"})
+        assert res.status_code == 200
+        data = res.json()
+        assert data["routing_mode"] == "mono"
+        mock_pipeline.set_routing.assert_called_with("mono", 7)
+
+    def test_set_routing_breakpoint(self, client, mock_pipeline):
+        """POST /api/routing sets breakpoint position."""
+        res = client.post("/api/routing", json={"routing_breakpoint": 3})
+        assert res.status_code == 200
+        data = res.json()
+        assert data["routing_breakpoint"] == 3
+        mock_pipeline.set_routing.assert_called_with("mono", 3)
+
+    def test_set_routing_both(self, client, mock_pipeline):
+        """POST /api/routing sets both mode and breakpoint."""
+        res = client.post("/api/routing", json={
+            "routing_mode": "4cm",
+            "routing_breakpoint": 5,
+        })
+        assert res.status_code == 200
+        data = res.json()
+        assert data["routing_mode"] == "4cm"
+        assert data["routing_breakpoint"] == 5
+        mock_pipeline.set_routing.assert_called_with("4cm", 5)
+
+    def test_set_routing_no_deps(self, client_no_deps):
+        """POST /api/routing returns 503 when pipeline not connected."""
+        res = client_no_deps.post("/api/routing", json={"routing_mode": "4cm"})
+        assert res.status_code == 503