avoid infinite loop in Tangle.precedes()

lib/msg-v4/tangle.js

@@ -296,13 +296,19 @@ class Tangle {
     if (msgAID === msgBID) return false
     if (msgBID === this.#rootID) return false
     let toCheck = [msgBID]
+    const checked = new Set()
     while (toCheck.length > 0) {
       const checking = /** @type {string} */ (toCheck.shift())
+      checked.add(checking)
       const prev = this.#prev.get(checking)
       if (!prev) continue
-      if (prev.includes(msgAID)) return true
-      toCheck.push(...prev)
+      if (prev.includes(msgAID)) {
+        checked.clear()
+        return true
+      }
+      toCheck.push(...prev.filter((p) => !checked.has(p)))
     }
+    checked.clear()
     return false
   }