refactor(ui-core): move ping state into PingEngine

Single in-flight ping + last result move from UITask to
ui-core/PingEngine.h; MyMesh's ping callback routes to the engine
instead of casting the Listener back to UITask. UITask keeps thin
wrappers (and the "not supported" alert), NearbyScreen is unchanged.

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

examples/companion_radio/ui-core/PingEngine.h

@@ -0,0 +1,76 @@
+#pragma once
+// Ping engine: one on-device ping in flight at a time (MyMesh::sendPing), its
+// result (RTT + SNR both ways) kept after the in-flight slot is released so the
+// view can keep showing it. The reply arrives through MyMesh's ping callback,
+// which is a plain function pointer -- routed here via a single static instance.
+//
+// The ping timeout is still decided by the view (NearbyScreen's
+// PING_TIMEOUT_MS), which calls clear() when it gives up.
+
+class PingEngine {
+public:
+  enum StartResult : uint8_t { STARTED = 0, BUSY, UNSUPPORTED, SEND_FAILED };
+
+  void begin(NodePrefs* prefs) { _prefs = prefs; s_instance = this; }
+
+  StartResult start(const uint8_t* pub_key) {
+    if (_active || !pub_key) return BUSY;
+    if (_prefs && _prefs->path_hash_mode > 1) return UNSUPPORTED;   // no 3-byte path hash support
+
+    _active = true;
+    _tag = 0;
+    _snr_out_x4 = 0;
+    _snr_back_x4 = 0;
+    _rtt_ms = 0;
+
+    // Always install the callback before sending so the response cannot race it.
+    the_mesh.setPingCallback(onPingResult, NULL);
+    _tag = the_mesh.sendPing(pub_key, _prefs ? _prefs->path_hash_mode + 1 : 1);
+    if (_tag == 0) {
+      clear();
+      return SEND_FAILED;
+    }
+    return STARTED;
+  }
+
+  // Release the in-flight slot (result values are kept).
+  void clear() {
+    if (_tag != 0) the_mesh.clearPingResult(_tag);
+    _active = false;
+    _tag = 0;
+  }
+
+  bool isActive() const { return _active; }
+  void getResult(int16_t& snr_out_x4, int16_t& snr_back_x4, uint32_t& rtt_ms) const {
+    snr_out_x4 = _snr_out_x4;
+    snr_back_x4 = _snr_back_x4;
+    rtt_ms = _rtt_ms;
+  }
+
+private:
+  void handleResult(uint32_t tag, int16_t snr_out_x4, int16_t snr_back_x4, uint32_t rtt_ms) {
+    if (_active && _tag == tag) {
+      _snr_out_x4 = snr_out_x4;
+      _snr_back_x4 = snr_back_x4;
+      _rtt_ms = rtt_ms;
+      // Release the in-flight slot immediately; the view keeps the result values.
+      clear();
+    }
+  }
+
+  static void onPingResult(uint32_t tag, int16_t snr_out_x4, int16_t snr_back_x4, uint32_t rtt_ms) {
+    if (s_instance) s_instance->handleResult(tag, snr_out_x4, snr_back_x4, rtt_ms);
+  }
+
+  static PingEngine* s_instance;
+
+  NodePrefs* _prefs = nullptr;
+  bool     _active = false;
+  uint32_t _tag = 0;
+  int16_t  _snr_out_x4 = 0;
+  int16_t  _snr_back_x4 = 0;
+  uint32_t _rtt_ms = 0;
+};
+
+// Header-only Core, single TU (see UiCore.h) -- the one definition lives here.
+PingEngine* PingEngine::s_instance = nullptr;

examples/companion_radio/ui-core/UiCore.h

@@ -11,11 +11,13 @@
 #include "DmUnreadTable.h"
 #include "UiEvents.h"
 #include "ClockEngine.h"
+#include "PingEngine.h"
 
 class UiCore {
 public:
   void begin(NodePrefs* prefs) {
     clock.begin(prefs, &events);
+    ping.begin(prefs);
   }
 
   // Driven from the frontend's loop(), before it drains `events`.
@@ -27,6 +29,7 @@ public:
 
   // ── Engines ───────────────────────────────────────────────────────────────
   ClockEngine clock;        // alarm / countdown / ring
+  PingEngine  ping;         // single in-flight ping + last result
 
   // ── Models ────────────────────────────────────────────────────────────────
   MessageHistory history;   // channel + DM rings, delivery state, channel unread