fix: only let wifiStrength broadcasts move the RSSI baseline

The emit to a newly connected client also stored the RSSI and time, which
restarted the 10s hold-off and hid a real change from the clients already
connected.  The baseline moves into RssiBroadcast, which ignores
per-client emits, with unit tests.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/ESPNetwork.cpp

@@ -180,8 +180,8 @@ bool ESPNetwork::changeAP(const uint8_t *bssid, const int32_t channel) {
 void ESPNetwork::emitSockets() {
   this->emitHeap();
   if(this->needsBroadcast ||
-    (this->connType == conn_types_t::wifi && rssiNeedsEmit(WiFi.RSSI(), this->lastRSSI, WiFi.channel(), this->lastChannel,
-      millis() - this->lastRSSIEmit, RSSI_EMIT_MIN_DBM, RSSI_EMIT_MIN_MS))) {
+    (this->connType == conn_types_t::wifi &&
+      this->rssiBroadcast.due(WiFi.RSSI(), WiFi.channel(), millis(), RSSI_EMIT_MIN_DBM, RSSI_EMIT_MIN_MS))) {
     this->emitSockets(255);
     sockEmit.loop();
     this->needsBroadcast = false;
@@ -209,9 +209,7 @@ void ESPNetwork::emitSockets(uint8_t num) {
         json->addElem("channel", (int32_t)this->channel);
         json->endObject();
         sockEmit.endEmit(num);
-        this->lastRSSI = WiFi.RSSI();
-        this->lastChannel = WiFi.channel();
-        this->lastRSSIEmit = millis();
+        this->rssiBroadcast.sent(num == 255, WiFi.RSSI(), WiFi.channel(), millis());
       }
       else {
         JsonSockEvent *json = sockEmit.beginEmit("wifiStrength");
@@ -229,9 +227,7 @@ void ESPNetwork::emitSockets(uint8_t num) {
         json->addElem("fullduplex", false);
         json->endObject();
         sockEmit.endEmit(num);
-        this->lastRSSI = -100;
-        this->lastChannel = -1;
-        this->lastRSSIEmit = millis();
+        this->rssiBroadcast.sent(num == 255, -100, -1, millis());
       }
   }
   // A broadcast comes from emitSockets(), which has already sent memStatus.

src/ESPNetwork.h

@@ -1,5 +1,6 @@
 #include <Arduino.h>
 #include <WiFi.h>
+#include "Utils.h"
 
 #ifndef ESPNetwork_h
 #define ESPNetwork_h
@@ -21,9 +22,7 @@ class ESPNetwork {
   protected:
     unsigned long lastEmit = 0;
     unsigned long lastMDNS = 0;
-    unsigned long lastRSSIEmit = 0;
-    int lastRSSI = 0;
-    int lastChannel = 0;
+    RssiBroadcast rssiBroadcast;
     int linkSpeed = 0;
     bool _connecting = false;
   public:

src/Utils.cpp

@@ -135,3 +135,12 @@ bool rssiNeedsEmit(int rssi, int lastRssi, int channel, int lastChannel, uint32_
   int delta = rssi > lastRssi ? rssi - lastRssi : lastRssi - rssi;
   return delta >= minDelta && sinceLastMs >= minMs;
 }
+bool RssiBroadcast::due(int rssi, int channel, uint32_t now, int minDelta, uint32_t minMs) const {
+  return rssiNeedsEmit(rssi, this->rssi, channel, this->channel, now - this->at, minDelta, minMs);
+}
+void RssiBroadcast::sent(bool broadcast, int rssi, int channel, uint32_t now) {
+  if(!broadcast) return;
+  this->rssi = rssi;
+  this->channel = channel;
+  this->at = now;
+}

src/Utils.h

@@ -60,6 +60,15 @@ struct rebootDelay_t {
 // otherwise only for an RSSI change of at least minDelta dBm and not more often
 // than every minMs.
 bool rssiNeedsEmit(int rssi, int lastRssi, int channel, int lastChannel, uint32_t sinceLastMs, int minDelta, uint32_t minMs);
+// What the last wifiStrength broadcast told every client.  Only broadcasts
+// move it: an emit to one new client tells the others nothing.
+struct RssiBroadcast {
+  int rssi = 0;
+  int channel = 0;
+  uint32_t at = 0;  // millis() of the last broadcast.
+  bool due(int rssi, int channel, uint32_t now, int minDelta, uint32_t minMs) const;
+  void sent(bool broadcast, int rssi, int channel, uint32_t now);
+};
 
 class Timestamp {
   char _timeBuffer[128];