feat(concord): make joined-list a registered Event (13302) for cache/account use

Promote the kind-13302 joined-communities list to a proper Event subclass so the
Android LocalCache/Account layer can observe it the way RelayGroupListState
observes SimpleGroupListEvent (10009):

- ConcordCommunityListEvent : Event — createAddress (13302, pubkey, ""), a
  suspend create(signer, entries), and decrypt(signer); content stays NIP-44
  self-encrypted and carries each community's secrets
- register the kind in EventFactory so inbound events parse to the typed class
- extract encode/decode JSON helpers in ConcordCommunityList (shared by both)

Test: create -> the wire form hides the name, a JSON round-trip resolves to the
typed class via EventFactory, decrypt recovers entries, and the replaceable
address is (13302, pubkey, ""). Green on :quartz:jvmTest.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CzJ2Cwo8tg4oZq43oRa3ig

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/concord/cord02Community/ConcordCommunityList.kt

@@ -78,11 +78,21 @@ object ConcordCommunityList {
         entries: List<ConcordCommunityListEntry>,
         createdAt: Long,
     ): Event {
-        val json = ConcordJson.instance.encodeToString(ListSerializer(ConcordCommunityListEntry.serializer()), entries)
-        val content = signer.nip44Encrypt(json, signer.pubKey)
+        val content = signer.nip44Encrypt(encode(entries), signer.pubKey)
         return signer.sign(createdAt, ConcordKinds.COMMUNITY_LIST, emptyArray(), content)
     }
 
+    /** Serializes [entries] to the plaintext JSON that gets NIP-44 self-encrypted. */
+    fun encode(entries: List<ConcordCommunityListEntry>): String = ConcordJson.instance.encodeToString(ListSerializer(ConcordCommunityListEntry.serializer()), entries)
+
+    /** Parses the decrypted plaintext JSON back into entries, or empty on failure. */
+    fun decode(json: String): List<ConcordCommunityListEntry> =
+        try {
+            ConcordJson.instance.decodeFromString(ListSerializer(ConcordCommunityListEntry.serializer()), json)
+        } catch (_: Exception) {
+            emptyList()
+        }
+
     /** Decrypts and parses a kind-13302 list event with [signer], or empty on failure. */
     suspend fun parse(
         event: Event,
@@ -90,8 +100,7 @@ object ConcordCommunityList {
     ): List<ConcordCommunityListEntry> {
         if (event.kind != ConcordKinds.COMMUNITY_LIST) return emptyList()
         return try {
-            val json = signer.nip44Decrypt(event.content, signer.pubKey)
-            ConcordJson.instance.decodeFromString(ListSerializer(ConcordCommunityListEntry.serializer()), json)
+            decode(signer.nip44Decrypt(event.content, signer.pubKey))
         } catch (_: Exception) {
             emptyList()
         }

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/concord/cord02Community/ConcordCommunityListEvent.kt

@@ -0,0 +1,79 @@
+/*
+ * 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.concord.cord02Community
+
+import androidx.compose.runtime.Immutable
+import com.vitorpamplona.quartz.concord.events.ConcordKinds
+import com.vitorpamplona.quartz.nip01Core.core.Address
+import com.vitorpamplona.quartz.nip01Core.core.Event
+import com.vitorpamplona.quartz.nip01Core.core.HexKey
+import com.vitorpamplona.quartz.nip01Core.signers.NostrSigner
+import com.vitorpamplona.quartz.utils.TimeUtils
+
+/**
+ * The member's private, self-encrypted list of joined Concord communities (kind
+ * [ConcordKinds.COMMUNITY_LIST] = 13302, CORD-05). A replaceable event whose
+ * `content` is the NIP-44 self-encryption of the [ConcordCommunityListEntry] JSON
+ * — including each community's secrets (`community_root`, salt, epoch,
+ * private-channel keys), so a single event both syncs membership across devices
+ * and carries the keys needed to re-derive every plane.
+ *
+ * This is the Concord analog of NIP-29's kind-10009 `SimpleGroupListEvent` and
+ * NIP-17's chatroom home base; it is what the Account's `ConcordChannelListState`
+ * observes. Only the owner's key decrypts it, so relays store ciphertext.
+ */
+@Immutable
+class ConcordCommunityListEvent(
+    id: HexKey,
+    pubKey: HexKey,
+    createdAt: Long,
+    tags: Array<Array<String>>,
+    content: String,
+    sig: HexKey,
+) : Event(id, pubKey, createdAt, KIND, tags, content, sig) {
+    override fun isContentEncoded() = true
+
+    /** Decrypts this list's entries with [signer], or empty on failure / wrong key. */
+    suspend fun decrypt(signer: NostrSigner): List<ConcordCommunityListEntry> =
+        try {
+            ConcordCommunityList.decode(signer.nip44Decrypt(content, signer.pubKey))
+        } catch (_: Exception) {
+            emptyList()
+        }
+
+    companion object {
+        const val KIND = ConcordKinds.COMMUNITY_LIST
+        const val ALT = "Private list of joined Concord communities"
+
+        /** The replaceable coordinate for a member's list: `(13302, pubkey, "")`. */
+        fun createAddress(pubKey: HexKey) = Address(KIND, pubKey, "")
+
+        /** Builds a signed, self-encrypted list event from [entries]. */
+        suspend fun create(
+            signer: NostrSigner,
+            entries: List<ConcordCommunityListEntry>,
+            createdAt: Long = TimeUtils.now(),
+        ): ConcordCommunityListEvent {
+            val content = signer.nip44Encrypt(ConcordCommunityList.encode(entries), signer.pubKey)
+            return signer.sign(createdAt, KIND, emptyArray(), content)
+        }
+    }
+}

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

@@ -22,6 +22,7 @@
 
 package com.vitorpamplona.quartz.utils
 
+import com.vitorpamplona.quartz.concord.cord02Community.ConcordCommunityListEvent
 import com.vitorpamplona.quartz.experimental.agora.FundraiserEvent
 import com.vitorpamplona.quartz.experimental.attestations.attestation.AttestationEvent
 import com.vitorpamplona.quartz.experimental.attestations.proficiency.AttestorProficiencyEvent
@@ -603,6 +604,7 @@ class EventFactory {
                 RootSiteEvent.KIND -> RootSiteEvent(id, pubKey, createdAt, tags, content, sig)
                 RepostEvent.KIND -> RepostEvent(id, pubKey, createdAt, tags, content, sig)
                 RequestToVanishEvent.KIND -> RequestToVanishEvent(id, pubKey, createdAt, tags, content, sig)
+                ConcordCommunityListEvent.KIND -> ConcordCommunityListEvent(id, pubKey, createdAt, tags, content, sig)
                 SealedRumorEvent.KIND -> SealedRumorEvent(id, pubKey, createdAt, tags, content, sig)
                 SearchRelayListEvent.KIND -> SearchRelayListEvent(id, pubKey, createdAt, tags, content, sig)
                 SimpleGroupListEvent.KIND -> SimpleGroupListEvent(id, pubKey, createdAt, tags, content, sig)

quartz/src/commonTest/kotlin/com/vitorpamplona/quartz/concord/cord02Community/ConcordCommunityListEventTest.kt

@@ -0,0 +1,70 @@
+/*
+ * 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.concord.cord02Community
+
+import com.vitorpamplona.quartz.nip01Core.core.Event
+import com.vitorpamplona.quartz.nip01Core.crypto.KeyPair
+import com.vitorpamplona.quartz.nip01Core.signers.NostrSignerInternal
+import kotlinx.coroutines.test.runTest
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertIs
+import kotlin.test.assertTrue
+
+class ConcordCommunityListEventTest {
+    private val signer = NostrSignerInternal(KeyPair())
+
+    private val entry =
+        ConcordCommunityListEntry(
+            id = "11".repeat(32),
+            owner = "0f".repeat(32),
+            ownerSalt = "aa".repeat(32),
+            root = "bb".repeat(32),
+            rootEpoch = 0,
+            relays = listOf("wss://relay.example"),
+            name = "Nostrichs",
+        )
+
+    @Test
+    fun eventFactoryReturnsTypedClassAndDecrypts() =
+        runTest {
+            val event = ConcordCommunityListEvent.create(signer, listOf(entry), createdAt = 1L)
+            assertEquals(ConcordCommunityListEvent.KIND, event.kind)
+            assertTrue(!event.content.contains("Nostrichs")) // encrypted on the wire
+
+            // A round-trip through JSON parsing resolves to the typed class via EventFactory.
+            val reparsed = Event.fromJson(event.toJson())
+            assertIs<ConcordCommunityListEvent>(reparsed)
+
+            val entries = reparsed.decrypt(signer)
+            assertEquals(1, entries.size)
+            assertEquals("Nostrichs", entries[0].name)
+            assertEquals(listOf("wss://relay.example"), entries[0].relays)
+        }
+
+    @Test
+    fun replaceableAddressIsKindPubkeyEmpty() {
+        val addr = ConcordCommunityListEvent.createAddress(signer.pubKey)
+        assertEquals(ConcordCommunityListEvent.KIND, addr.kind)
+        assertEquals(signer.pubKey, addr.pubKeyHex)
+        assertEquals("", addr.dTag)
+    }
+}