feat: add recipientPubKeys()/groupMembers() helpers and multi-device docs

- Add recipientPubKeys() and groupMembers() helper methods to
  CallAnswerEvent, CallHangupEvent, CallRejectEvent, and
  CallRenegotiateEvent (matching the existing pattern in CallOfferEvent)
- Document in NIP-AC spec that group calls handle multi-device
  self-notification implicitly by including the sender's own pubkey
  in the gift-wrap recipient set

https://claude.ai/code/session_013h2E7spwHDgSjunqumsYgp

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nipACWebRtcCalls/NIP-AC.md

@@ -353,6 +353,8 @@ When a user is logged in on multiple devices, all devices will receive and ring
 
 These self-notification events use the same `call-id` as the original call and follow the same gift-wrapping rules. Clients receiving a self-addressed answer or reject MUST verify the `call-id` matches the currently ringing call before acting on it.
 
+**Group calls**: In group calls, the sender's own pubkey SHOULD be included in the set of recipients when gift-wrapping answer and reject events. This means the self-notification is implicit — no separate self-addressed event is needed. The same signed inner event (with all group member `p` tags) is simply wrapped to the sender's own pubkey along with all other members.
+
 ### Audio and Media
 
 - Clients SHOULD switch `AudioManager` to `MODE_IN_COMMUNICATION` when a call connects and restore to `MODE_NORMAL` when the call ends.

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nipACWebRtcCalls/events/CallAnswerEvent.kt

@@ -25,6 +25,7 @@ import com.vitorpamplona.quartz.nip01Core.core.Event
 import com.vitorpamplona.quartz.nip01Core.core.HexKey
 import com.vitorpamplona.quartz.nip01Core.core.TagArrayBuilder
 import com.vitorpamplona.quartz.nip01Core.signers.eventTemplate
+import com.vitorpamplona.quartz.nip01Core.tags.people.PTag
 import com.vitorpamplona.quartz.nip01Core.tags.people.pTag
 import com.vitorpamplona.quartz.nip01Core.tags.people.pTagIds
 import com.vitorpamplona.quartz.nip31Alts.alt
@@ -46,6 +47,12 @@ class CallAnswerEvent(
 
     fun sdpAnswer() = content
 
+    /** All pubkeys referenced by `p` tags in this event. */
+    fun recipientPubKeys(): Set<HexKey> = tags.mapNotNull(PTag::parseKey).toSet()
+
+    /** All group members: `p`-tagged pubkeys plus the event author. */
+    fun groupMembers(): Set<HexKey> = recipientPubKeys().plus(pubKey)
+
     companion object {
         const val KIND = 25051
         const val ALT_DESCRIPTION = "WebRTC call answer"

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nipACWebRtcCalls/events/CallHangupEvent.kt

@@ -25,6 +25,7 @@ import com.vitorpamplona.quartz.nip01Core.core.Event
 import com.vitorpamplona.quartz.nip01Core.core.HexKey
 import com.vitorpamplona.quartz.nip01Core.core.TagArrayBuilder
 import com.vitorpamplona.quartz.nip01Core.signers.eventTemplate
+import com.vitorpamplona.quartz.nip01Core.tags.people.PTag
 import com.vitorpamplona.quartz.nip01Core.tags.people.pTag
 import com.vitorpamplona.quartz.nip01Core.tags.people.pTagIds
 import com.vitorpamplona.quartz.nip31Alts.alt
@@ -46,6 +47,12 @@ class CallHangupEvent(
 
     fun reason() = content.ifEmpty { null }
 
+    /** All pubkeys referenced by `p` tags in this event. */
+    fun recipientPubKeys(): Set<HexKey> = tags.mapNotNull(PTag::parseKey).toSet()
+
+    /** All group members: `p`-tagged pubkeys plus the event author. */
+    fun groupMembers(): Set<HexKey> = recipientPubKeys().plus(pubKey)
+
     companion object {
         const val KIND = 25053
         const val ALT_DESCRIPTION = "WebRTC call hangup"

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nipACWebRtcCalls/events/CallRejectEvent.kt

@@ -25,6 +25,7 @@ import com.vitorpamplona.quartz.nip01Core.core.Event
 import com.vitorpamplona.quartz.nip01Core.core.HexKey
 import com.vitorpamplona.quartz.nip01Core.core.TagArrayBuilder
 import com.vitorpamplona.quartz.nip01Core.signers.eventTemplate
+import com.vitorpamplona.quartz.nip01Core.tags.people.PTag
 import com.vitorpamplona.quartz.nip01Core.tags.people.pTag
 import com.vitorpamplona.quartz.nip01Core.tags.people.pTagIds
 import com.vitorpamplona.quartz.nip31Alts.alt
@@ -46,6 +47,12 @@ class CallRejectEvent(
 
     fun reason() = content.ifEmpty { null }
 
+    /** All pubkeys referenced by `p` tags in this event. */
+    fun recipientPubKeys(): Set<HexKey> = tags.mapNotNull(PTag::parseKey).toSet()
+
+    /** All group members: `p`-tagged pubkeys plus the event author. */
+    fun groupMembers(): Set<HexKey> = recipientPubKeys().plus(pubKey)
+
     companion object {
         const val KIND = 25054
         const val ALT_DESCRIPTION = "WebRTC call rejection"

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nipACWebRtcCalls/events/CallRenegotiateEvent.kt

@@ -25,6 +25,7 @@ import com.vitorpamplona.quartz.nip01Core.core.Event
 import com.vitorpamplona.quartz.nip01Core.core.HexKey
 import com.vitorpamplona.quartz.nip01Core.core.TagArrayBuilder
 import com.vitorpamplona.quartz.nip01Core.signers.eventTemplate
+import com.vitorpamplona.quartz.nip01Core.tags.people.PTag
 import com.vitorpamplona.quartz.nip01Core.tags.people.pTag
 import com.vitorpamplona.quartz.nip01Core.tags.people.pTagIds
 import com.vitorpamplona.quartz.nip31Alts.alt
@@ -46,6 +47,12 @@ class CallRenegotiateEvent(
 
     fun sdpOffer() = content
 
+    /** All pubkeys referenced by `p` tags in this event. */
+    fun recipientPubKeys(): Set<HexKey> = tags.mapNotNull(PTag::parseKey).toSet()
+
+    /** All group members: `p`-tagged pubkeys plus the event author. */
+    fun groupMembers(): Set<HexKey> = recipientPubKeys().plus(pubKey)
+
     companion object {
         const val KIND = 25055
         const val ALT_DESCRIPTION = "WebRTC call renegotiation"