feat(l2,core): battery curve editor and an L2 feedback round

- Battery curve: NodePrefs batt_curve_mv[11] (voltage at 0..100 %, all
  zeros = built-in LiPo curve, sentinel 0xC0DE0032). ui-core/Battery.h
  uses it for every percentage. L1: Settings > System > Batt curve list
  (Left/Right 10 mV, Reset); L2: Settings > Power > Battery curve chart
  with draggable points and a line at the cell's voltage.
- L2: the Nodes map is the full navigation map plus the nodes, Back
  returns to Nodes; the favourite button is lit while it is one; pinning
  to the Home dial uses a thumbtack (fonts regenerated); minimap dots
  follow the accent; arranging tiles shows where they land while dragging;
  emoji row in Diagnostics > Font.
- Sim hooks: sim_open nodesmap / accent@N / homeedit / battcurve.

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

examples/companion_radio/ui-new/BatteryCurveScreen.h

@@ -0,0 +1,80 @@
+#pragma once
+#include "InfoKit.h"
+#include "../ui-core/Battery.h"
+// Settings › System › Battery curve: the cell voltage at 0, 10, ... 100 %
+// (NodePrefs::batt_curve_mv, ui-core/Battery.h). Left/Right move the selected
+// point 10 mV, kept between its neighbours; the first change copies the
+// built-in curve in, Reset goes back to it. "Now" shows the cell as read, to
+// set a point against. Saved on the way out.
+// Included by UITask.cpp after AutoAdvertScreen.h.
+
+class BatteryCurveScreen : public UIScreen {
+  UITask*    _task;
+  NodePrefs* _prefs;
+  int  _sel = 1, _scroll = 0;
+  bool _dirty = false;
+
+  static const int PTS = battery::CURVE_PTS;
+  static const int ROWS = 1 + PTS + 1;   // Now, the points, Reset
+  static const int STEP_MV = 10;
+
+  void nudge(int i, int d) {
+    uint16_t* c = _prefs->batt_curve_mv;
+    if (!battery::validCurve(c))
+      for (int k = 0; k < PTS; k++) c[k] = (uint16_t)battery::builtinMvAt(k);
+    const int lo = i > 0       ? c[i - 1] + STEP_MV : battery::CURVE_MIN_MV;
+    const int hi = i < PTS - 1 ? c[i + 1] - STEP_MV : battery::CURVE_MAX_MV;
+    c[i] = (uint16_t)constrain((int)c[i] + d * STEP_MV, lo, hi);
+    _dirty = true;
+  }
+
+public:
+  BatteryCurveScreen(UITask* task, NodePrefs* prefs) : _task(task), _prefs(prefs) {}
+
+  void onShow() override { _sel = 1; _scroll = 0; _dirty = false; }
+
+  int render(DisplayDriver& display) override {
+    display.setTextSize(1);
+    display.setColor(DisplayDriver::LIGHT);
+    drawScreenHeader(display, "Battery curve");
+    const int mv = _task->getBattMilliVolts();
+    const bool custom = _prefs && battery::validCurve(_prefs->batt_curve_mv);
+    drawList(display, ROWS, _sel, _scroll, [&](int i, int y, bool sel, int reserve) {
+      drawRowSelection(display, y, sel, reserve);
+      char l[12], v[20];
+      if (i == 0) {
+        strcpy(l, "Now");
+        snprintf(v, sizeof(v), "%d mV %d%%", mv, battery::rawPercent(mv));
+      } else if (i <= PTS) {
+        snprintf(l, sizeof(l), "%d%%", (i - 1) * 10);
+        snprintf(v, sizeof(v), "%d mV", battery::curveMvAt(i - 1));
+      } else {
+        strcpy(l, "Reset");
+        strcpy(v, custom ? "" : "LiPo");   // the built-in curve is the one in use
+      }
+      info::valueRow(display, y, l, v, sel, reserve);
+    });
+    return 1000;   // "Now" follows the cell
+  }
+
+  bool handleInput(char c) override {
+    if (c == KEY_CANCEL) {
+      _task->savePrefsIfDirty(_dirty);
+      _task->gotoSettingsScreen();
+      return true;
+    }
+    if (c == KEY_UP)   { if (_sel > 0) _sel--; return true; }
+    if (c == KEY_DOWN) { if (_sel < ROWS - 1) _sel++; return true; }
+    if (!_prefs) return false;
+    if (_sel >= 1 && _sel <= PTS && (keyIsNext(c) || keyIsPrev(c))) {
+      nudge(_sel - 1, keyIsNext(c) ? 1 : -1);
+      return true;
+    }
+    if (_sel == ROWS - 1 && c == KEY_ENTER && battery::validCurve(_prefs->batt_curve_mv)) {
+      memset(_prefs->batt_curve_mv, 0, sizeof(_prefs->batt_curve_mv));
+      _dirty = true;
+      return true;
+    }
+    return false;
+  }
+};

examples/companion_radio/ui-new/SettingsScreen.h

@@ -9,6 +9,7 @@
 #include "AccordionList.h"
 #include "PopupMenu.h"   // scope list management's per-row action menu
 #include "InfoKit.h"     // value / switch rows
+#include "../ui-core/Battery.h"   // the Battery curve row
 
 class SettingsScreen : public UIScreen {
   UITask* _task;
@@ -49,6 +50,7 @@ class SettingsScreen : public UIScreen {
     SECTION_SYSTEM,
     DEVICE_NAME,
     SCHEMA_SYSTEM,    // power, units
+    BATT_CURVE,
     REBOOT,
     // Keyboard section
     SECTION_KEYBOARD,
@@ -78,6 +80,7 @@ class SettingsScreen : public UIScreen {
   int  _selected = 0;   // SettingItem under the cursor, resolved per input/render
   int  _reserve = 0;    // right-edge px reserved for the scrollbar (0 when list fits)
   bool _dirty = false;
+  bool _keep_place = false;   // set when opening a screen from a row, so Back lands on it
 
   AccordionList _acc;
   static const int NUM_SECTIONS = 8;
@@ -512,6 +515,8 @@ class SettingsScreen : public UIScreen {
       sw("Lock PIN", _task->passwordLockEnabled());
     } else if (item == DEVICE_NAME) {
       val("Name", the_mesh.getNodeName());
+    } else if (item == BATT_CURVE) {
+      val("Batt curve", p && battery::validCurve(p->batt_curve_mv) ? "Custom" : "LiPo");
     } else if (item == REBOOT) {
       display.print("Reboot");   // action row: Enter reboots this device
     } else if (item == KEYBOARD_TYPE) {
@@ -629,6 +634,8 @@ public:
 
 
   void onShow() override {
+    const bool keep = _keep_place;   // back from a screen opened here: same row
+    _keep_place = false;
     _dirty = false;
     _edit_name = false;
     _scope_mgmt_active = false;
@@ -638,7 +645,7 @@ public:
     _prune_confirm.active = false;
     _edit_lock_pass = false;
     _lock_pass_first[0] = '\0';
-    resetList();
+    if (!keep) resetList();
     _editor.freq.active = false;
   }
 
@@ -981,6 +988,12 @@ public:
       _scope_mgmt_scroll = 0;
       return true;
     }
+    if (_selected == BATT_CURVE && enter) {
+      _keep_place = true;   // back from it to this row, not a folded list
+      _task->savePrefsIfDirty(_dirty);
+      _task->gotoBatteryCurve();
+      return true;
+    }
     if (_selected == REBOOT && enter) {
       _task->showAlert("Rebooting...", 800);
       _task->shutdown(true);   // flushes prefs/RTC/contacts/trail, then reboots -- single choke point

examples/companion_radio/ui-new/UITask.cpp

@@ -177,6 +177,7 @@ static void fmtAlt(char* buf, int n, float meters, bool imperial) {
 #include "NearbyScreen.h"
 #include "DashboardConfigScreen.h"
 #include "AutoAdvertScreen.h"
+#include "BatteryCurveScreen.h"
 #include "LiveShareScreen.h"
 #include "LocatorScreen.h"
 #include "TrailScreen.h"
@@ -1623,6 +1624,7 @@ void UITask::begin(DisplayDriver* display, SensorManager* sensors, NodePrefs* no
   _sensors = sensors;
   _node_prefs = node_prefs;
   _kb.prefs = node_prefs;
+  if (node_prefs) battery::useCurve(node_prefs->batt_curve_mv);   // Settings > Battery curve
   uint32_t aoff = autoOffMillis();
   _auto_off = millis() + (aoff > 0 ? aoff : AUTO_OFF_MILLIS);
 
@@ -1719,6 +1721,7 @@ void UITask::begin(DisplayDriver* display, SensorManager* sensors, NodePrefs* no
   nearby_screen = new NearbyScreen(this);
   dashboard_config = new DashboardConfigScreen(this, node_prefs);
   auto_advert_screen = new AutoAdvertScreen(this, node_prefs);
+  batt_curve_screen = new BatteryCurveScreen(this, node_prefs);
   live_share_screen = new LiveShareScreen(this, node_prefs);
   locator_screen  = new LocatorScreen(this, node_prefs);
   trail_screen       = new TrailScreen(this, &_core->trail.store());
@@ -1853,6 +1856,7 @@ void UITask::gotoMapScreen() {
 
 void UITask::gotoLocatorScreen()    { setCurrScreen(locator_screen); }
 void UITask::gotoAutoAdvertScreen() { setCurrScreen(auto_advert_screen); }
+void UITask::gotoBatteryCurve() { setCurrScreen(batt_curve_screen); }
 
 bool UITask::startPing(const uint8_t* pub_key) {
   PingEngine::StartResult r = _core->ping.start(pub_key);

examples/companion_radio/ui-new/UITask.h

@@ -112,6 +112,7 @@ class UITask : public UITaskBase, public UiCoreHost {
   UIScreen* nearby_screen = nullptr;
   UIScreen* dashboard_config = nullptr;
   UIScreen* auto_advert_screen = nullptr;
+  UIScreen* batt_curve_screen = nullptr;
   UIScreen* live_share_screen = nullptr;
   UIScreen* locator_screen = nullptr;
   UIScreen* trail_screen = nullptr;
@@ -287,6 +288,7 @@ public:
   void gotoNearbyScreen();
   void gotoDashboardConfig();
   void gotoAutoAdvertScreen();
+  void gotoBatteryCurve();   // Settings > System > Battery curve
   void gotoLiveShareScreen();
   // Live share session control (ui-core/LiveShareEngine.h): restart = new
   // session (re-announce + fresh clock); clock-only = changed "Stop after".