Treat finished PCB review as complete, not a raw SSE error.

The status watcher synthesized pcb_error with pcb_status=complete (terminal)
when the worker finished before pcb_complete arrived. Map that hatch to
pcb_complete, publish the event before flipping status, and send /pcb to
the layout report tree.

tests/test_pcb_sse_terminal.py

@@ -0,0 +1,43 @@
+"""PCB SSE terminal mapping — complete is not pcb_error."""
+
+from backend.services.pcb_pipeline import pcb_sse_terminal_from_status
+
+
+def test_complete_status_is_pcb_complete_not_error():
+    ev, data = pcb_sse_terminal_from_status(
+        "complete",
+        {"findings": 38, "domains": 3, "groups": 4},
+        "pcb_status=complete (terminal)",
+    )
+    assert ev == "pcb_complete"
+    assert data["findings"] == 38
+    assert data["domains"] == 3
+    assert data["groups"] == 4
+    assert "error" not in data
+
+
+def test_complete_reason_without_status_still_completes():
+    ev, data = pcb_sse_terminal_from_status(
+        "running",
+        {},
+        "pcb_status=complete (terminal)",
+    )
+    assert ev == "pcb_complete"
+    assert data.get("synthetic") is True
+
+
+def test_error_status_stays_pcb_error():
+    ev, data = pcb_sse_terminal_from_status(
+        "error",
+        {"error": "parse failed"},
+        "pcb_status=error (terminal)",
+    )
+    assert ev == "pcb_error"
+    assert data["error"] == "parse failed"
+
+
+def test_cancelled_status_is_pcb_cancelled():
+    ev, _data = pcb_sse_terminal_from_status(
+        "cancelled", {}, "pcb_status=cancelled (terminal)",
+    )
+    assert ev == "pcb_cancelled"