refactor: extract popup menu into reusable PopupMenu struct with wrap-around navigation

- Add PopupMenu.h: generic scrollable overlay with wrap-around nav (up from
  first wraps to last, down from last wraps to first), closes on ENTER or
  CANCEL/CONTEXT_MENU. Default constructor ensures active=false on creation.
- KeyboardWidget: replace inline placeholder overlay (~50 lines) with PopupMenu
- UITask QuickMsgScreen: replace inline context menus in CONTACT_PICK and
  CHANNEL_PICK with PopupMenu; notif label stored in _ctx_notif_item at open time
- BotScreen: clear placeholder list for trigger field (placeholders are
  expansion tokens that would never match incoming literal text)
- MsgExpand: fix APPEND macro off-by-one (oi+_l < out_len-1 → < out_len)

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

examples/companion_radio/ui-new/PopupMenu.h

@@ -0,0 +1,90 @@
+#pragma once
+#include <helpers/ui/DisplayDriver.h>
+#include <Arduino.h>
+
+// Generic scrollable popup menu overlay.
+// Caller owns item string lifetimes — addItem() stores const char* pointers.
+// Navigation wraps around: up from first item goes to last, and vice versa.
+struct PopupMenu {
+  static const int PM_MAX_ITEMS = 16;
+  static const int PM_BX        = 12;
+  static const int PM_BY        = 10;
+  static const int PM_BW        = 104;
+  static const int PM_ITEM_H    = 10;
+
+  const char* _items[PM_MAX_ITEMS];
+  int         _count;
+  int         _sel;
+  int         _scroll;
+  int         _visible;
+  bool        active;
+  const char* _title;
+
+  enum Result { NONE, SELECTED, CANCELLED };
+
+  PopupMenu() : _count(0), _sel(0), _scroll(0), _visible(3), active(false), _title(nullptr) {}
+
+  void begin(const char* title, int visible = 3) {
+    _count = 0; _sel = 0; _scroll = 0;
+    _visible = visible; active = true; _title = title;
+  }
+
+  void addItem(const char* item) {
+    if (_count < PM_MAX_ITEMS) _items[_count++] = item;
+  }
+
+  int render(DisplayDriver& display) {
+    int vis = (_count < _visible) ? _count : _visible;
+    int bh  = 12 + vis * PM_ITEM_H;
+
+    display.setColor(DisplayDriver::DARK);
+    display.fillRect(PM_BX, PM_BY, PM_BW, bh);
+    display.setColor(DisplayDriver::LIGHT);
+    display.drawRect(PM_BX, PM_BY, PM_BW, bh);
+    display.setCursor(PM_BX + 4, PM_BY + 1);
+    display.print(_title);
+    display.fillRect(PM_BX, PM_BY + 10, PM_BW, 1);
+
+    if (_scroll > 0)
+      { display.setCursor(PM_BX + PM_BW - 7, PM_BY + 1); display.print("^"); }
+    if (_scroll + vis < _count)
+      { display.setCursor(PM_BX + PM_BW - 7, PM_BY + 2 + vis * PM_ITEM_H); display.print("v"); }
+
+    for (int i = 0; i < vis && (_scroll + i) < _count; i++) {
+      int idx = _scroll + i;
+      int py  = PM_BY + 12 + i * PM_ITEM_H;
+      if (idx == _sel) {
+        display.setColor(DisplayDriver::LIGHT);
+        display.fillRect(PM_BX + 1, py - 1, PM_BW - 2, PM_ITEM_H);
+        display.setColor(DisplayDriver::DARK);
+      } else {
+        display.setColor(DisplayDriver::LIGHT);
+      }
+      display.setCursor(PM_BX + 4, py);
+      display.print(_items[idx]);
+    }
+    display.setColor(DisplayDriver::LIGHT);
+    return 50;
+  }
+
+  Result handleInput(char c) {
+    if (_count == 0) { active = false; return CANCELLED; }
+    if (c == KEY_UP) {
+      _sel = (_sel > 0) ? _sel - 1 : _count - 1;
+      if (_sel < _scroll)                                 _scroll = _sel;
+      else if (_sel == _count - 1 && _count > _visible)  _scroll = _count - _visible;
+      return NONE;
+    }
+    if (c == KEY_DOWN) {
+      _sel = (_sel < _count - 1) ? _sel + 1 : 0;
+      if (_sel >= _scroll + _visible)  _scroll = _sel - _visible + 1;
+      else if (_sel == 0)              _scroll = 0;
+      return NONE;
+    }
+    if (c == KEY_ENTER)                           { active = false; return SELECTED;  }
+    if (c == KEY_CANCEL || c == KEY_CONTEXT_MENU) { active = false; return CANCELLED; }
+    return NONE;
+  }
+
+  int selectedIndex() const { return _sel; }
+};