feat: add refinement snapshot API

cmd/sdrd/http_handlers.go

@@ -151,6 +151,19 @@ func registerAPIHandlers(mux *http.ServeMux, cfgPath string, cfgManager *runtime
 		}
 		_ = json.NewEncoder(w).Encode(recommend)
 	})
+	mux.HandleFunc("/api/refinement", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		snap := phaseSnap.Snapshot()
+		out := map[string]any{
+			"plan":       snap.refinementInput.Plan,
+			"windows":    snap.refinementInput.Windows,
+			"candidates": len(snap.refinementInput.Candidates),
+			"scheduled":  len(snap.refinementInput.Scheduled),
+			"signals":    len(snap.refinement.Signals),
+			"decisions":  len(snap.refinement.Decisions),
+		}
+		_ = json.NewEncoder(w).Encode(out)
+	})
 	mux.HandleFunc("/api/events", func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("Content-Type", "application/json")
 		limit := 200