fix(node): respect display units for position ground speed (#6376)

Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>

Author: jamesarich

.skills/compose-ui/strings-index.txt

@@ -22,6 +22,7 @@ import org.meshtastic.core.common.util.MeasurementSystem
 import org.meshtastic.core.common.util.formatString
 import org.meshtastic.core.common.util.getSystemMeasurementSystem
 import org.meshtastic.proto.Config.DisplayConfig.DisplayUnits
+import kotlin.math.roundToInt
 
 @Suppress("MagicNumber")
 enum class DistanceUnit(val symbol: String, val multiplier: Float, val system: Int) {
@@ -90,6 +91,15 @@ fun Float.toSpeedString(system: DisplayUnits): String = if (system == DisplayUni
     formatString("%.0f mph", this * 2.23694f)
 }
 
+/**
+ * Converts a speed already expressed in km/h (e.g. protobuf `Position.ground_speed`) to [system]'s unit, rounded to a
+ * whole number. Callers render the result through a localized string resource so the unit label itself stays
+ * translatable (see `speed_kmh`/`speed_mph`).
+ */
+@Suppress("MagicNumber")
+fun Int.kmhIn(system: DisplayUnits): Int =
+    if (system == DisplayUnits.IMPERIAL) (this * 0.621371f).roundToInt() else this
+
 @Suppress("MagicNumber")
 fun Float.toSmallDistanceString(system: DisplayUnits): String = if (system == DisplayUnits.IMPERIAL) {
     formatString("%.2f in", this / 25.4f)

core/model/src/commonMain/kotlin/org/meshtastic/core/model/util/DistanceExtensions.kt

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2026 Meshtastic LLC
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+package org.meshtastic.core.model.util
+
+import org.meshtastic.proto.Config.DisplayConfig.DisplayUnits
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class DistanceExtensionsTest {
+
+    @Test
+    fun `kmhIn returns value unchanged for metric`() {
+        assertEquals(50, 50.kmhIn(DisplayUnits.METRIC))
+    }
+
+    @Test
+    fun `kmhIn converts to mph for imperial`() {
+        assertEquals(31, 50.kmhIn(DisplayUnits.IMPERIAL))
+        assertEquals(50, 80.kmhIn(DisplayUnits.IMPERIAL))
+    }
+
+    @Test
+    fun `kmhIn handles zero`() {
+        assertEquals(0, 0.kmhIn(DisplayUnits.METRIC))
+        assertEquals(0, 0.kmhIn(DisplayUnits.IMPERIAL))
+    }
+}

core/model/src/commonTest/kotlin/org/meshtastic/core/model/util/DistanceExtensionsTest.kt

@@ -1592,6 +1592,7 @@
     <string name="soil_temperature">Soil Temp</string>
     <string name="speed">Speed</string>
     <string name="speed_kmh">%1$d Km/h</string>
+    <string name="speed_mph">%1$d mph</string>
     <string name="spread_factor">Spread Factor</string>
     <string name="ssid">SSID</string>
     <string name="state_broadcast_seconds">State broadcast (seconds)</string>

core/resources/src/commonMain/composeResources/values/strings.xml

@@ -41,6 +41,7 @@ import org.meshtastic.core.common.util.formatString
 import org.meshtastic.core.model.util.GeoConstants.DEG_D
 import org.meshtastic.core.model.util.GeoConstants.HEADING_DEG
 import org.meshtastic.core.model.util.TimeConstants.MS_PER_SEC
+import org.meshtastic.core.model.util.kmhIn
 import org.meshtastic.core.model.util.metersIn
 import org.meshtastic.core.model.util.toString
 import org.meshtastic.core.resources.Res
@@ -50,6 +51,7 @@ import org.meshtastic.core.resources.latitude
 import org.meshtastic.core.resources.longitude
 import org.meshtastic.core.resources.sats
 import org.meshtastic.core.resources.speed_kmh
+import org.meshtastic.core.resources.speed_mph
 import org.meshtastic.core.ui.theme.GraphColors
 import org.meshtastic.proto.Config
 import org.meshtastic.proto.Position
@@ -127,9 +129,15 @@ fun PositionCard(
                     )
                     if (position.ground_speed != null && position.ground_speed != 0) {
                         Spacer(Modifier.width(12.dp))
+                        val speedRes =
+                            if (displayUnits == Config.DisplayConfig.DisplayUnits.IMPERIAL) {
+                                Res.string.speed_mph
+                            } else {
+                                Res.string.speed_kmh
+                            }
                         MetricValueRow(
                             color = GraphColors.Gold,
-                            text = stringResource(Res.string.speed_kmh, position.ground_speed ?: 0),
+                            text = stringResource(speedRes, (position.ground_speed ?: 0).kmhIn(displayUnits)),
                         )
                     }
                 }