fix(dm): convert @npub mentions to nostr: URIs in NIP-17 messages

The NIP-17 DM composer sent the typed text verbatim, so an `@npub1…`
mention went out as plain text instead of a `nostr:nprofile1…` reference.
Run the message through NewMessageTagger like every other composer, but
use only the rewritten content: its pTags are not added to the event,
because a NIP-17 room is defined by its p-tags and tagging a mentioned
user would move the message into a different conversation.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019JSYZ3DdZJXvv4vh4vw4G9

commons/src/jvmTest/kotlin/com/vitorpamplona/amethyst/commons/model/composer/NewMessageTaggerKeyParseTest.kt

@@ -209,4 +209,15 @@ class NewMessageTaggerKeyParseTest {
 
             assertTrue(tagger.message.startsWith("hi nostr:nprofile1"))
         }
+
+    @Test
+    fun possessiveAtMentionBecomesNostrUri() =
+        runBlocking {
+            val npub = "npub19ma2w9dmk3kat0nt0k5dwuqzvmg3va9ezwup0zkakhpwv0vcwvcsg8axkl"
+            val tagger = NewMessageTagger(message = "@$npub's ERP screens look good", dao = dao)
+            tagger.run()
+
+            val nprofile = tagger.pTags!!.single().toNProfile()
+            assertEquals("nostr:$nprofile's ERP screens look good", tagger.message)
+        }
 }

commonsUI/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/ui/screen/loggedIn/chats/privateDM/send/ChatNewMessageViewModel.kt

@@ -603,7 +603,13 @@ class ChatNewMessageViewModel :
     ) {
         val room = room.value ?: return
 
-        val messageText = message.text.toString()
+        // Rewrites typed `@npub…`/`note1…` references into `nostr:` URIs. Only the rewritten text is
+        // used: the tagger's pTags must NOT reach the event, since a NIP-17 room is defined by its
+        // p-tags — adding a mentioned user would send the message to a different conversation.
+        val tagger = NewMessageTagger(message.text.toString(), null, null, accountViewModel)
+        tagger.run()
+
+        val messageText = tagger.message
         val urls = findURLs(messageText)
         val usedAttachments = iMetaAttachments.filterIsIn(urls.toSet())
         val emojis = accountViewModel.account.emoji.findEmojiTags(messageText)