feat: add EphemeralGiftWrapEvent (kind 21059)

Adds an ephemeral variant of GiftWrap for transient encrypted messages
that relays don't need to persist. EphemeralGiftWrapEvent extends
GiftWrapEvent so all existing processing paths (decryption, routing,
notifications, call signaling) automatically handle it via type
hierarchy. Relay subscription filters are updated to request both kinds.

https://claude.ai/code/session_0157X96G6HLTzYxkdX9pyTSJ

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/subscriptions/FilterBuilders.kt

@@ -21,6 +21,8 @@
 package com.vitorpamplona.amethyst.desktop.subscriptions
 
 import com.vitorpamplona.quartz.nip01Core.relay.filters.Filter
+import com.vitorpamplona.quartz.nip59Giftwrap.wraps.EphemeralGiftWrapEvent
+import com.vitorpamplona.quartz.nip59Giftwrap.wraps.GiftWrapEvent
 
 /**
  * Type-safe builders for common Nostr filter patterns.
@@ -540,7 +542,7 @@ object FilterBuilders {
         since: Long? = null,
     ): Filter =
         Filter(
-            kinds = listOf(1059), // GiftWrapEvent.KIND
+            kinds = listOf(GiftWrapEvent.KIND, EphemeralGiftWrapEvent.KIND),
             tags = mapOf("p" to listOf(pubKeyHex)),
             since = since,
         )

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/subscriptions/FilterDMs.kt

@@ -25,6 +25,7 @@ import com.vitorpamplona.quartz.nip01Core.core.HexKey
 import com.vitorpamplona.quartz.nip01Core.relay.filters.Filter
 import com.vitorpamplona.quartz.nip01Core.relay.normalizer.NormalizedRelayUrl
 import com.vitorpamplona.quartz.nip04Dm.messages.PrivateDmEvent
+import com.vitorpamplona.quartz.nip59Giftwrap.wraps.EphemeralGiftWrapEvent
 import com.vitorpamplona.quartz.nip59Giftwrap.wraps.GiftWrapEvent
 import com.vitorpamplona.quartz.utils.TimeUtils
 
@@ -126,7 +127,7 @@ object FilterDMs {
         since: Long? = null,
     ): Filter =
         Filter(
-            kinds = listOf(GiftWrapEvent.KIND),
+            kinds = listOf(GiftWrapEvent.KIND, EphemeralGiftWrapEvent.KIND),
             tags = mapOf("p" to listOf(userPubKeyHex)),
             since = since?.minus(TimeUtils.twoDays()),
         )