feat(ios): derive treadmill speed from Apple Watch cadence in Fake Treadmill mode

Adds opt-in setting `applewatch_as_treadmill_speed` (default off) that
derives Speed from Apple Watch step cadence inside cadenceFromAppleWatch()
when fakedevice_treadmill is also enabled. Reuses cadence_sensor_speed_ratio
("Wheel Ratio") for the multiplier and the existing virtual treadmill / RSC
broadcast pipeline. Useful for indoor walking and slow jogging with apps like
Kinomap or Zwift when no physical treadmill is connected.

Dual-gated behind both new toggles so normal treadmill users are unaffected.
When cadence reports exactly zero (user stopped), Speed is also zeroed; a
negative cadence (no fresh sample) leaves Speed unchanged. Settings appended
at the end of qzsettings and settings.qml per src/CLAUDE.md.

Author: miraicat

src/devices/treadmill.cpp

@@ -612,11 +612,31 @@ bool treadmill::cadenceFromAppleWatch() {
                    .startsWith(QStringLiteral("Disabled"))) {
         long appleWatchCadence = h.stepCadence();
         qDebug() << QStringLiteral("Current Cadence: ") << QString::number(appleWatchCadence);
+        // Slow-jogging mode: derive Speed from Apple Watch cadence when running on Fake
+        // Treadmill. Gated on both toggles so this only runs in the explicit Fake Treadmill
+        // use case and does not affect normal treadmill users by default.
+        const bool appleWatchTreadmillSpeed =
+            settings.value(QZSettings::applewatch_as_treadmill_speed,
+                           QZSettings::default_applewatch_as_treadmill_speed).toBool() &&
+            settings.value(QZSettings::fakedevice_treadmill,
+                           QZSettings::default_fakedevice_treadmill).toBool();
         if (appleWatchCadence > 0) {
             evaluateStepCount();
             Cadence = appleWatchCadence;
+            if (appleWatchTreadmillSpeed) {
+                const double ratio =
+                    settings.value(QZSettings::cadence_sensor_speed_ratio,
+                                   QZSettings::default_cadence_sensor_speed_ratio).toDouble();
+                Speed = appleWatchCadence * (ratio > 0.0 ? ratio : 0.0);
+            }
             return true;
         }
+        if (appleWatchCadence == 0 && appleWatchTreadmillSpeed) {
+            // Cadence reported as exactly zero (user stopped); zero Speed too so the virtual
+            // treadmill broadcast doesn't ghost the previous value. Negative values are
+            // treated as "no fresh sample" and leave Speed unchanged.
+            Speed = 0;
+        }
         return false;
     }
 #endif

src/qzsettings.cpp

@@ -1081,9 +1081,10 @@ const QString QZSettings::step_gain = QStringLiteral("step_gain");
 const QString QZSettings::proform_carbon_tlx_treadmill = QStringLiteral("proform_carbon_tlx_treadmill");
 const QString QZSettings::proform_carbon_tlx_v84_314_treadmill = QStringLiteral("proform_carbon_tlx_v84_314_treadmill");
 const QString QZSettings::proform_carbon_tl_PFTL59723_6 = QStringLiteral("proform_carbon_tl_PFTL59723_6");
+const QString QZSettings::applewatch_as_treadmill_speed = QStringLiteral("applewatch_as_treadmill_speed");
 
 
-const uint32_t allSettingsCount = 882;
+const uint32_t allSettingsCount = 883;
 
 QVariant allSettings[allSettingsCount][2] = {
     {QZSettings::cryptoKeySettingsProfiles, QZSettings::default_cryptoKeySettingsProfiles},
@@ -1989,6 +1990,7 @@ QVariant allSettings[allSettingsCount][2] = {
     {QZSettings::proform_carbon_tlx_treadmill, QZSettings::default_proform_carbon_tlx_treadmill},
     {QZSettings::proform_carbon_tlx_v84_314_treadmill, QZSettings::default_proform_carbon_tlx_v84_314_treadmill},
     {QZSettings::proform_carbon_tl_PFTL59723_6, QZSettings::default_proform_carbon_tl_PFTL59723_6},
+    {QZSettings::applewatch_as_treadmill_speed, QZSettings::default_applewatch_as_treadmill_speed},
 };
 
 void QZSettings::qDebugAllSettings(bool showDefaults) {

src/qzsettings.h

@@ -2974,6 +2974,15 @@ class QZSettings {
     static const QString proform_carbon_tl_PFTL59723_6;
     static constexpr bool default_proform_carbon_tl_PFTL59723_6 = false;
 
+    /**
+     * @brief When enabled together with fakedevice_treadmill, derives treadmill Speed from
+     * Apple Watch step cadence using cadence_sensor_speed_ratio. Lets users do indoor walking
+     * or slow jogging without a physical treadmill, broadcasting cadence-driven speed via
+     * the existing virtual treadmill / RSC pipeline. Default off; iOS-only effect.
+     */
+    static const QString applewatch_as_treadmill_speed;
+    static constexpr bool default_applewatch_as_treadmill_speed = false;
+
     /**
      * @brief Write the QSettings values using the constants from this namespace.
      * @param showDefaults Optionally indicates if the default should be shown with the key.

src/settings.qml

@@ -1313,6 +1313,7 @@ import Qt.labs.platform 1.1
             property double power_sensor_speed_inclination_coeff_a: 0.0
             property double power_sensor_speed_inclination_coeff_b: 0.0
             property bool proform_carbon_tlx_v84_314_treadmill: false
+            property bool applewatch_as_treadmill_speed: false
         }
 
 
@@ -14497,6 +14498,34 @@ import Qt.labs.platform 1.1
                         color: Material.color(Material.Lime)
                     }
 
+                    IndicatorOnlySwitch {
+                        id: appleWatchAsTreadmillSpeedDelegate
+                        text: qsTr("Use Apple Watch Cadence for Fake Treadmill Speed")
+                        spacing: 0
+                        bottomPadding: 0
+                        topPadding: 0
+                        rightPadding: 0
+                        leftPadding: 0
+                        clip: false
+                        checked: settings.applewatch_as_treadmill_speed
+                        Layout.alignment: Qt.AlignLeft | Qt.AlignTop
+                        Layout.fillWidth: true
+                        onClicked: { settings.applewatch_as_treadmill_speed = checked; window.settings_restart_to_apply = true; }
+                    }
+
+                    Label {
+                        text: qsTr("iOS only. For Fake Treadmill mode: when no physical treadmill is connected, derives Speed from Apple Watch step cadence using the Wheel Ratio under Accessories > Cadence Sensor Options. For walking or slow jogging, set Wheel Ratio much lower than the cycling default, usually around 0.025-0.04. Useful with apps like Kinomap or Zwift. Default is off.")
+                        font.bold: true
+                        font.italic: true
+                        font.pixelSize: Qt.application.font.pixelSize - 2
+                        textFormat: Text.PlainText
+                        wrapMode: Text.WordWrap
+                        verticalAlignment: Text.AlignVCenter
+                        Layout.alignment: Qt.AlignLeft | Qt.AlignTop
+                        Layout.fillWidth: true
+                        color: Material.color(Material.Lime)
+                    }
+
                     IndicatorOnlySwitch {
                         id: fakeEllipticalDelegate
                         text: qsTr("Fake Elliptical")