fix(sessions): nil map panic in updateSandboxSummary goroutine

r.Context() is cancelled when HTTP handler returns; fetchEntitySummary
returns nil on cancelled context. Two fixes:
1. Detached request with context.Background() for the goroutine call
2. Nil guard on current before map assignment

internal/sessions/handler.go

@@ -582,8 +582,17 @@ func (h *Handler) handleSandboxCreate(w http.ResponseWriter, r *http.Request, se
 }
 
 // updateSandboxSummary merges pod/svc metadata into the session memory_entity (fire-and-forget).
+// Uses context.Background() because r.Context() is cancelled once the HTTP handler returns.
 func (h *Handler) updateSandboxSummary(r *http.Request, sessionID, podName, pvcName, svcDns string) {
-	current, _ := h.fetchEntitySummary(r, "session-"+sessionID, sessionID, "SESSION")
+	// Build a detached request carrying just the auth header.
+	detached, _ := http.NewRequestWithContext(context.Background(), r.Method, r.URL.String(), nil)
+	if auth := r.Header.Get("Authorization"); auth != "" {
+		detached.Header.Set("Authorization", auth)
+	}
+	current, _ := h.fetchEntitySummary(detached, "session-"+sessionID, sessionID, "SESSION")
+	if current == nil {
+		current = map[string]any{}
+	}
 	current["pod_name"] = podName
 	current["svc_dns"] = svcDns
 	current["last_active_at"] = time.Now().UTC().Format(time.RFC3339)