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.

backend/routers/pipeline.py

@@ -892,16 +892,16 @@ async def pcb_events(project_id: str, request: Request):
 
             if crash_detected["reason"] is not None:
                 cur = proj_svc.get_project(storage, owner_user_id, project_id)
-                err = None
-                if cur and cur.pcb_state:
-                    err = cur.pcb_state.get("error")
+                from backend.services.pcb_pipeline import pcb_sse_terminal_from_status
+
+                ev, payload = pcb_sse_terminal_from_status(
+                    cur.pcb_status if cur else None,
+                    cur.pcb_state if cur else None,
+                    crash_detected["reason"],
+                )
                 yield {
-                    "event": "pcb_error",
-                    "data": json.dumps({
-                        "error": err or crash_detected["reason"]
-                        or "pcb worker terminated without a terminal event",
-                        "synthetic": True,
-                    }),
+                    "event": ev,
+                    "data": json.dumps(payload),
                 }
         finally:
             watcher.cancel()