fix: move ContentResolver.getType off main thread in share intent consumer

The DisposableEffect's OnNewIntentListener is invoked on the main thread
  when a new ACTION_SEND intent arrives (e.g. SwiftKey sharing a GIF). It
  called contentResolver.getType() synchronously, which can Binder-IPC to
  a remote content provider and block for tens to hundreds of milliseconds.

  Use rememberCoroutineScope() + scope.launch(Dispatchers.IO) since
  DisposableEffect has no coroutine scope of its own. The scope is tied to
  composition and cancels cleanly on disposal.

  Also fix a latent bug: the consumer read activity.intent instead of the
  intent parameter passed into the callback. activity.intent is the
  Activity's launch intent, not the new one that triggered the listener,
  so subsequent intents would reuse the first intent's URI.

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/home/ShortNotePostScreen.kt

@@ -55,6 +55,7 @@ import androidx.compose.runtime.Composable
 import androidx.compose.runtime.DisposableEffect
 import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.collectAsState
+import androidx.compose.runtime.rememberCoroutineScope
 import androidx.compose.ui.Alignment.Companion.CenterVertically
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.platform.LocalContext
@@ -124,6 +125,7 @@ import kotlinx.collections.immutable.persistentListOf
 import kotlinx.collections.immutable.toImmutableList
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.FlowPreview
+import kotlinx.coroutines.launch
 import kotlinx.coroutines.withContext
 
 @OptIn(ExperimentalMaterial3Api::class, FlowPreview::class)
@@ -144,6 +146,7 @@ fun ShortNotePostScreen(
 
     val context = LocalContext.current
     val activity = context.getActivity()
+    val scope = rememberCoroutineScope()
 
     LaunchedEffect(Unit) {
         postViewModel.initWritingAssistant(context)
@@ -177,9 +180,12 @@ fun ShortNotePostScreen(
                         postViewModel.addToMessage(it)
                     }
 
-                    IntentCompat.getParcelableExtra(activity.intent, Intent.EXTRA_STREAM, Uri::class.java)?.let {
-                        val mediaType = context.contentResolver.getType(it)
-                        postViewModel.selectImage(persistentListOf(SelectedMedia(it, mediaType)))
+                    // Use the `intent` parameter (the new intent), not activity.intent (the launch intent).
+                    IntentCompat.getParcelableExtra(intent, Intent.EXTRA_STREAM, Uri::class.java)?.let { uri ->
+                        scope.launch(Dispatchers.IO) {
+                            val mediaType = context.contentResolver.getType(uri)
+                            postViewModel.selectImage(persistentListOf(SelectedMedia(uri, mediaType)))
+                        }
                     }
                 }
             }