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

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip59Giftwrap/wraps/EphemeralGiftWrapEvent.kt

@@ -0,0 +1,87 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.quartz.nip59Giftwrap.wraps
+
+import androidx.compose.runtime.Immutable
+import com.vitorpamplona.quartz.nip01Core.core.Event
+import com.vitorpamplona.quartz.nip01Core.core.HexKey
+import com.vitorpamplona.quartz.nip01Core.crypto.KeyPair
+import com.vitorpamplona.quartz.nip01Core.signers.NostrSignerSync
+import com.vitorpamplona.quartz.nip01Core.tags.people.PTag
+import com.vitorpamplona.quartz.nip40Expiration.ExpirationTag
+import com.vitorpamplona.quartz.utils.TimeUtils
+
+@Immutable
+class EphemeralGiftWrapEvent(
+    id: HexKey,
+    pubKey: HexKey,
+    createdAt: Long,
+    tags: Array<Array<String>>,
+    content: String,
+    sig: HexKey,
+) : GiftWrapEvent(id, pubKey, createdAt, tags, content, sig, KIND) {
+    override fun copyNoContent(): EphemeralGiftWrapEvent {
+        val copy =
+            EphemeralGiftWrapEvent(
+                id,
+                pubKey,
+                createdAt,
+                tags,
+                "",
+                sig,
+            )
+
+        copy.innerEventId = innerEventId
+
+        return copy
+    }
+
+    companion object {
+        const val KIND = 21059
+        const val ALT = "Ephemeral encrypted event"
+
+        fun create(
+            event: Event,
+            recipientPubKey: HexKey,
+            expirationDelta: Long? = null,
+            createdAt: Long = TimeUtils.randomWithTwoDays(),
+        ): EphemeralGiftWrapEvent {
+            val signer = NostrSignerSync(KeyPair())
+
+            val tags =
+                expirationDelta?.let {
+                    arrayOf(
+                        PTag.assemble(recipientPubKey, null),
+                        ExpirationTag.assemble(createdAt + it + TimeUtils.twoDays()),
+                    )
+                } ?: arrayOf(
+                    PTag.assemble(recipientPubKey, null),
+                )
+
+            return signer.sign(
+                createdAt = createdAt,
+                kind = KIND,
+                tags = tags,
+                content = signer.nip44Encrypt(event.toJson(), recipientPubKey),
+            )
+        }
+    }
+}

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip59Giftwrap/wraps/GiftWrapEvent.kt

@@ -36,19 +36,20 @@ import com.vitorpamplona.quartz.utils.Log
 import com.vitorpamplona.quartz.utils.TimeUtils
 
 @Immutable
-class GiftWrapEvent(
+open class GiftWrapEvent(
     id: HexKey,
     pubKey: HexKey,
     createdAt: Long,
     tags: Array<Array<String>>,
     content: String,
     sig: HexKey,
-) : Event(id, pubKey, createdAt, KIND, tags, content, sig) {
+    kind: Int = KIND,
+) : Event(id, pubKey, createdAt, kind, tags, content, sig) {
     @kotlinx.serialization.Transient
     @kotlin.jvm.Transient
     var innerEventId: HexKey? = null
 
-    fun copyNoContent(): GiftWrapEvent {
+    open fun copyNoContent(): GiftWrapEvent {
         val copy =
             GiftWrapEvent(
                 id,

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/utils/EventFactory.kt

@@ -159,6 +159,7 @@ import com.vitorpamplona.quartz.nip58Badges.award.BadgeAwardEvent
 import com.vitorpamplona.quartz.nip58Badges.definition.BadgeDefinitionEvent
 import com.vitorpamplona.quartz.nip58Badges.profile.ProfileBadgesEvent
 import com.vitorpamplona.quartz.nip59Giftwrap.seals.SealedRumorEvent
+import com.vitorpamplona.quartz.nip59Giftwrap.wraps.EphemeralGiftWrapEvent
 import com.vitorpamplona.quartz.nip59Giftwrap.wraps.GiftWrapEvent
 import com.vitorpamplona.quartz.nip5aStaticWebsites.NamedSiteEvent
 import com.vitorpamplona.quartz.nip5aStaticWebsites.RootSiteEvent
@@ -384,6 +385,7 @@ class EventFactory {
                 GenericRepostEvent.KIND -> GenericRepostEvent(id, pubKey, createdAt, tags, content, sig)
                 GeohashListEvent.KIND -> GeohashListEvent(id, pubKey, createdAt, tags, content, sig)
                 GiftWrapEvent.KIND -> GiftWrapEvent(id, pubKey, createdAt, tags, content, sig)
+                EphemeralGiftWrapEvent.KIND -> EphemeralGiftWrapEvent(id, pubKey, createdAt, tags, content, sig)
                 GitAuthorListEvent.KIND -> GitAuthorListEvent(id, pubKey, createdAt, tags, content, sig)
                 GitRepositoryListEvent.KIND -> GitRepositoryListEvent(id, pubKey, createdAt, tags, content, sig)
                 GitIssueEvent.KIND -> GitIssueEvent(id, pubKey, createdAt, tags, content, sig)