feat: introduce Desktop target and expand Kotlin Multiplatform (KMP) architecture (#4761)

Signed-off-by: James Rich <2199651+jamesarich@users.noreply.github.com>

core/navigation/src/commonMain/kotlin/org/meshtastic/core/navigation/TopLevelDestination.kt

@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2025-2026 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.navigation
+
+import androidx.navigation3.runtime.NavKey
+import org.jetbrains.compose.resources.StringResource
+import org.meshtastic.core.resources.Res
+import org.meshtastic.core.resources.bottom_nav_settings
+import org.meshtastic.core.resources.connections
+import org.meshtastic.core.resources.conversations
+import org.meshtastic.core.resources.map
+import org.meshtastic.core.resources.nodes
+
+/**
+ * Shared top-level destinations for the application shell.
+ *
+ * Defines the canonical set of destinations and their corresponding labels and routes, ensuring parity between Android
+ * and Desktop navigation shells.
+ */
+enum class TopLevelDestination(val label: StringResource, val route: Route) {
+    Conversations(Res.string.conversations, ContactsRoutes.ContactsGraph),
+    Nodes(Res.string.nodes, NodesRoutes.NodesGraph),
+    Map(Res.string.map, MapRoutes.Map()),
+    Settings(Res.string.bottom_nav_settings, SettingsRoutes.SettingsGraph()),
+    Connections(Res.string.connections, ConnectionsRoutes.ConnectionsGraph),
+    ;
+
+    companion object {
+        fun fromNavKey(key: NavKey?): TopLevelDestination? =
+            entries.find { dest -> key?.let { it::class == dest.route::class } == true }
+    }
+}

core/navigation/src/commonTest/kotlin/org/meshtastic/core/navigation/NavigationParityTest.kt

@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2025-2026 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.navigation
+
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertNotNull
+
+class NavigationParityTest {
+
+    @Test
+    fun `all top level destinations are defined`() {
+        assertEquals(5, TopLevelDestination.entries.size)
+    }
+
+    @Test
+    fun `fromNavKey matches all top level routes`() {
+        TopLevelDestination.entries.forEach { destination ->
+            val result = TopLevelDestination.fromNavKey(destination.route)
+            assertNotNull(result, "Should match destination for route ${destination.route}")
+            assertEquals(destination, result)
+        }
+    }
+}