fix: saved tracks overlay, GPX file handler, nav import

Saved tracks overlay was immediately hidden after showing because
bottomNav.selectedItemId = nav_map fires the nav item listener, which
calls hideOverlays(). Removed that line — the map tab is already
selected when the instrument sheet is open.

GPX file handler:
- Manifest: intent-filter for application/gpx+xml + singleTop launch
  mode so onNewIntent is called when app is already running
- MainActivity: handleIncomingGpx() called from onCreate + onNewIntent;
  parses the URI on IO dispatcher and hands points to ViewModel
- MainViewModel: addImportedTrack() prepends parsed points to pastTracks
  and savedTracks state flows (displayed in session only, not persisted)

https://claude.ai/code/session_01DNjbYxiC1cco83dArNGW3G

3 files changed, 44 insertions, 1 deletions

diff --git a/android-app/app/src/main/AndroidManifest.xml b/android-app/app/src/main/AndroidManifest.xml
index 7cbafc7..7b9a9e4 100644
--- a/android-app/app/src/main/AndroidManifest.xml
+++ b/android-app/app/src/main/AndroidManifest.xml
@@ -27,12 +27,18 @@
         <activity
             android:name=".MainActivity"
             android:exported="true"
+            android:launchMode="singleTop"
             android:screenOrientation="portrait"
             android:configChanges="orientation|screenSize">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />
                 <category android:name="android.intent.category.LAUNCHER" />
             </intent-filter>
+            <intent-filter>
+                <action android:name="android.intent.action.VIEW" />
+                <category android:name="android.intent.category.DEFAULT" />
+                <data android:mimeType="application/gpx+xml" />
+            </intent-filter>
         </activity>
     </application>
 </manifest>
diff --git a/android-app/app/src/main/kotlin/org/terst/nav/MainActivity.kt b/android-app/app/src/main/kotlin/org/terst/nav/MainActivity.kt
index 0df4069..10eb0a8 100644
--- a/android-app/app/src/main/kotlin/org/terst/nav/MainActivity.kt
+++ b/android-app/app/src/main/kotlin/org/terst/nav/MainActivity.kt
@@ -3,6 +3,10 @@ package org.terst.nav
 import android.Manifest
 import android.content.Intent
 import android.content.pm.PackageManager
+import android.util.Log
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.withContext
+import org.terst.nav.track.GpxParser
 import android.graphics.Bitmap
 import android.graphics.Canvas
 import android.media.MediaPlayer
@@ -127,6 +131,30 @@ class MainActivity : AppCompatActivity(), SafetyFragment.SafetyListener {
         unitPrefs = UnitPrefs(this)
         checkForegroundPermissions()
         initializeUI()
+        handleIncomingGpx(intent)
+    }
+
+    override fun onNewIntent(intent: Intent) {
+        super.onNewIntent(intent)
+        handleIncomingGpx(intent)
+    }
+
+    private fun handleIncomingGpx(intent: Intent?) {
+        if (intent?.action != Intent.ACTION_VIEW) return
+        val uri = intent.data ?: return
+        lifecycleScope.launch {
+            runCatching {
+                val points = withContext(Dispatchers.IO) {
+                    contentResolver.openInputStream(uri)?.use { GpxParser.parse(it) } ?: emptyList()
+                }
+                if (points.isNotEmpty()) {
+                    viewModel.addImportedTrack(points)
+                    showOverlay(SavedTracksFragment())
+                }
+            }.onFailure { e ->
+                Log.e("MainActivity", "Failed to open GPX: ${e.message}")
+            }
+        }
     }
 
     private fun initializeUI() {
@@ -242,7 +270,8 @@ class MainActivity : AppCompatActivity(), SafetyFragment.SafetyListener {
             showOverlay(SavedTracksFragment())
             bottomSheetBehavior.isHideable = true
             bottomSheetBehavior.state = BottomSheetBehavior.STATE_HIDDEN
-            bottomNav.selectedItemId = R.id.nav_map  // keep map tab highlighted
+            // Note: do NOT set selectedItemId here — it triggers the nav listener
+            // which calls hideOverlays(), immediately undoing showOverlay().
         }
     }
 
diff --git a/android-app/app/src/main/kotlin/org/terst/nav/ui/MainViewModel.kt b/android-app/app/src/main/kotlin/org/terst/nav/ui/MainViewModel.kt
index cc51dd1..dcbd98e 100644
--- a/android-app/app/src/main/kotlin/org/terst/nav/ui/MainViewModel.kt
+++ b/android-app/app/src/main/kotlin/org/terst/nav/ui/MainViewModel.kt
@@ -18,6 +18,7 @@ import org.terst.nav.track.SavedTrack
 import org.terst.nav.track.TrackPoint
 import org.terst.nav.track.TrackRepository
 import org.terst.nav.track.TrackStats
+import org.terst.nav.track.toSavedTrack
 import org.terst.nav.settings.FeatureFlags
 import org.terst.nav.settings.HardwareSource
 import org.terst.nav.vessel.CrewMember
@@ -410,6 +411,13 @@ class MainViewModel(
     fun selectTrack(track: SavedTrack) { _selectedTrack.value = track }
     fun clearSelectedTrack() { _selectedTrack.value = null }
 
+    /** Adds a track parsed from an external GPX file (not persisted to storage). */
+    fun addImportedTrack(points: List<TrackPoint>) {
+        val updated = _pastTracks.value.toMutableList().also { it.add(0, points) }
+        _pastTracks.value = updated
+        _savedTracks.value = updated.filter { it.isNotEmpty() }.map { it.toSavedTrack() }
+    }
+
     fun panToTrackPoint(lat: Double, lon: Double) {
         viewModelScope.launch { _panToPosition.emit(lat to lon) }
     }