feat: filter to ephemeral streams and particles

js/src/features/particles/particle-list-view.tsx

@@ -1,4 +1,4 @@
-import { useEffect, useMemo, useRef } from "react";
+import { useEffect, useMemo, useRef, useState } from "react";
 import { useNavigate } from "react-router-dom";
 import beepSound from "../../../assets/sound.wav";
 import {
@@ -28,6 +28,8 @@ import { Progress } from "@/components/ui/progress";
 import { Small } from "@/components/ui/typography";
 import type { Particle, StreamProperties } from "@/api/types";
 import { useAutoplayStore } from "@/stores/autoplay-store";
+import { where, Timestamp } from "firebase/firestore";
+import { RECENCY_WINDOW_HOURS } from "@/lib/constants";
 
 function getParticleTypeIcon(particle: Particle): LucideIcon {
   switch (particle.type) {
@@ -257,7 +259,23 @@ export function ParticleListView({ path }: ParticleListViewProps) {
   const user = useAuthStore((s) => s.user);
   const visibilityScopes = useVisibilityScopes(user?.email, networkId);
 
-  const { children, isLoading } = useLiveParticleChildren(path, "last_child_created_at", "desc", visibilityScopes);
+  const [recencyCutoff, setRecencyCutoff] = useState(() => {
+    const d = new Date();
+    d.setHours(d.getHours() - RECENCY_WINDOW_HOURS);
+    return Timestamp.fromDate(d);
+  });
+
+  // Refresh the cutoff every hour so streams don't vanish/appear stale
+  useEffect(() => {
+    const interval = setInterval(() => {
+      const d = new Date();
+      d.setHours(d.getHours() - RECENCY_WINDOW_HOURS);
+      setRecencyCutoff(Timestamp.fromDate(d));
+    }, 60 * 60 * 1000);
+    return () => clearInterval(interval);
+  }, []);
+
+  const { children, isLoading } = useLiveParticleChildren(path, "last_child_created_at", "desc", visibilityScopes, undefined, undefined, where("last_child_created_at", ">=", recencyCutoff));
   const navigate = useNavigate();
 
   const streams = useMemo(