feat(diag): reset-counters popup; harden repeater loop-detect bounds

- DiagnosticsScreen: Enter opens a confirm popup (defaults to Cancel) that
  zeroes the cumulative counters via Mesh::resetStats().
- Dispatcher::resetStats() made virtual; Mesh overrides it to also clear
  n_forwarded so the reset covers the repeater forward count.
- REPEAT_LOOP_MAX gains a 4-byte-hash entry and isRepeatLooped() bounds-
  checks hash_size, so it can't OOB-read if path_mode 3 is ever accepted.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

examples/companion_radio/MyMesh.cpp

@@ -525,7 +525,11 @@ bool MyMesh::filterRecvFloodPacket(mesh::Packet* packet) {
 // thresholds (max times this node's hash may already appear in the path, by hash size).
 // A companion moves around, so it re-enters its own flood's path more easily than a
 // fixed repeater — hardcoded rather than configurable since there's no CLI here.
-static const uint8_t REPEAT_LOOP_MAX[] = { 0, /*1-byte*/ 2, /*2-byte*/ 1, /*3-byte*/ 1 };
+// Indexed by getPathHashSize() = (path_len>>6)+1, so 1..4. Index 0 is unused
+// (hash size is never 0); index 4 covers path_mode 3, which tryParsePacket
+// currently rejects — kept in-bounds so this can't OOB-read if that guard is
+// ever relaxed.
+static const uint8_t REPEAT_LOOP_MAX[] = { 0, /*1-byte*/ 2, /*2-byte*/ 1, /*3-byte*/ 1, /*4-byte*/ 1 };
 // Caps how many hops an ADVERT flood gets repeated, matching simple_repeater's default
 // flood_max_advert — adverts are the most frequent flood traffic, so this is the one
 // depth limit worth keeping even without the rest of simple_repeater's flood_max knobs.
@@ -533,6 +537,7 @@ static const uint8_t REPEAT_MAX_ADVERT_HOPS = 8;
 
 bool MyMesh::isRepeatLooped(const mesh::Packet* packet) const {
   uint8_t hash_size = packet->getPathHashSize();
+  if (hash_size >= sizeof(REPEAT_LOOP_MAX)) return true;  // unknown hash size: treat as looped, don't forward
   uint8_t hash_count = packet->getPathHashCount();
   uint8_t n = 0;
   const uint8_t* path = packet->path;

examples/companion_radio/ui-new/DiagnosticsScreen.h

@@ -4,6 +4,7 @@
 #include <helpers/DeviceDiag.h>
 #include <Arduino.h>
 #include "icons.h"
+#include "PopupMenu.h"
 #include "../MyMesh.h"
 
 extern MyMesh the_mesh;
@@ -18,6 +19,7 @@ extern MyMesh the_mesh;
 class DiagnosticsScreen : public UIScreen {
   UITask* _task;
   int _scroll = 0;
+  PopupMenu _reset_menu;   // Enter → confirm before zeroing the cumulative counters
 
   struct Row { const char* label; char value[20]; };
   static const int MAX_ROWS = 13;
@@ -128,13 +130,31 @@ public:
     }
     drawScrollIndicator(display, start_y, visible * item_h, _row_count, visible, _scroll);
     display.setColor(DisplayDriver::LIGHT);
-    return 1000;   // stats refresh once a second — no need for a faster redraw
+    if (_reset_menu.active) _reset_menu.render(display);
+    return _reset_menu.active ? 50 : 1000;   // popup wants snappier redraw; stats otherwise refresh once a second
   }
 
   bool handleInput(char c) override {
+    if (_reset_menu.active) {
+      auto res = _reset_menu.handleInput(c);
+      // Index 0 = "Reset", 1 = "Cancel" (destructive option first, but never the
+      // default landing row — see setSelected below).
+      if (res == PopupMenu::SELECTED && _reset_menu.selectedIndex() == 0) {
+        the_mesh.resetStats();   // zeroes Dispatcher per-type counters + Mesh forward count
+        _task->showAlert("Counters reset", 800);
+      }
+      return true;
+    }
     if (c == KEY_UP)   { if (_scroll > 0) _scroll--; return true; }
     if (c == KEY_DOWN) { _scroll++; return true; }   // clamped to max_scroll in render()
-    if (c == KEY_CANCEL || c == KEY_CONTEXT_MENU || c == KEY_ENTER) { _task->gotoToolsScreen(); return true; }
+    if (c == KEY_ENTER) {
+      _reset_menu.begin("Reset counters?", 2);
+      _reset_menu.addItem("Reset");
+      _reset_menu.addItem("Cancel");
+      _reset_menu.setSelected(1);   // default to Cancel so a stray Enter doesn't wipe stats
+      return true;
+    }
+    if (c == KEY_CANCEL || c == KEY_CONTEXT_MENU) { _task->gotoToolsScreen(); return true; }
     return false;
   }
 };