feat(concord): let the owner dissolve a community

`dissolveConcordCommunity` existed with no UI caller, so an owner could
only dissolve a community from amy. Adds an owner-only "Dissolve
community" item beside Leave, with an irreversible-action confirmation.
Verified: amy and a live member see the community read-only.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

commonsUI/src/commonMain/composeResources/values/strings.xml

@@ -615,6 +615,11 @@
     <string name="concord_timer_notice_off">%1$s turned off disappearing messages</string>
     <string name="concord_timer_active">Messages disappear after %1$s</string>
     <string name="concord_dissolved_read_only">This community has been dissolved and is now read-only. You can still read its history, but no new messages can be posted.</string>
+    <string name="concord_dissolve_community">Dissolve community</string>
+    <string name="concord_dissolve_title">Dissolve %1$s?</string>
+    <string name="concord_dissolve_message">This ends the community for everyone. It becomes read-only: members keep its history, but nobody can post, change it, or invite anyone again. This can't be undone.</string>
+    <string name="concord_dissolve_confirm">Dissolve</string>
+    <string name="concord_dissolve_failed">The community was not dissolved: only its owner can, from an account that can sign.</string>
     <string name="concord_private_channel_no_key">This is a private channel and you don't hold its key, so you can't read it or post here.</string>
     <string name="concord_private_channel_cut">You no longer have access to this private channel: its key was rotated without you, so you can't read new messages or post here.</string>
     <string name="concord_banned_notice">You're banned from this community, so you can't post here and your messages are hidden from everyone.</string>

commonsUI/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/ui/screen/loggedIn/chats/publicChannels/concord/ConcordChannelListScreen.kt

@@ -95,6 +95,10 @@ import com.vitorpamplona.amethyst.commons.resources.concord_channel_rename_save
 import com.vitorpamplona.amethyst.commons.resources.concord_channel_rotate_key
 import com.vitorpamplona.amethyst.commons.resources.concord_channels_empty
 import com.vitorpamplona.amethyst.commons.resources.concord_direct_invite_action
+import com.vitorpamplona.amethyst.commons.resources.concord_dissolve_community
+import com.vitorpamplona.amethyst.commons.resources.concord_dissolve_confirm
+import com.vitorpamplona.amethyst.commons.resources.concord_dissolve_message
+import com.vitorpamplona.amethyst.commons.resources.concord_dissolve_title
 import com.vitorpamplona.amethyst.commons.resources.concord_edit_title
 import com.vitorpamplona.amethyst.commons.resources.concord_invite_action
 import com.vitorpamplona.amethyst.commons.resources.concord_invite_links_action
@@ -193,6 +197,7 @@ fun ConcordChannelListScreen(
     // Read once here (it is @Composable) so the post-leave navigation can use it from a callback.
     val canPop = nav.canPop()
     var showLeave by remember { mutableStateOf(false) }
+    var showDissolve by remember { mutableStateOf(false) }
     var showDirectInvite by remember { mutableStateOf(false) }
 
     if (showDirectInvite) {
@@ -217,6 +222,18 @@ fun ConcordChannelListScreen(
         )
     }
 
+    if (showDissolve) {
+        ConcordDissolveDialog(
+            communityName = communityName,
+            onDismiss = { showDissolve = false },
+            onConfirm = {
+                showDissolve = false
+                // Stay here: the dissolved community stays readable, and this screen shows it read-only.
+                accountViewModel.dissolveConcordCommunity(communityId)
+            },
+        )
+    }
+
     // Channel create/rename/delete are gated on MANAGE_CHANNELS (or owner) — the same predicate the
     // fold enforces, so an unauthorized action would be a silent no-op we shouldn't even offer.
     // Rank alone isn't enough on a split epoch: publishing any Control edition also takes the
@@ -416,6 +433,21 @@ fun ConcordChannelListScreen(
                                 showLeave = true
                             },
                         )
+                        // Owner only, like the verifiers: anyone else's tombstone is ignored (CORD-02 §9).
+                        if (isOwner && state?.dissolved != true) {
+                            DropdownMenuItem(
+                                text = {
+                                    Text(
+                                        stringRes(Res.string.concord_dissolve_community),
+                                        color = MaterialTheme.colorScheme.error,
+                                    )
+                                },
+                                onClick = {
+                                    menuOpen = false
+                                    showDissolve = true
+                                },
+                            )
+                        }
                     }
                 },
             )
@@ -728,6 +760,30 @@ fun ConcordLeaveDialog(
     )
 }
 
+/** Confirms dissolving a community (CORD-02 §9): irreversible, so the confirm button is the error color. */
+@Composable
+fun ConcordDissolveDialog(
+    communityName: String,
+    onDismiss: () -> Unit,
+    onConfirm: () -> Unit,
+) {
+    AlertDialog(
+        onDismissRequest = onDismiss,
+        title = { Text(stringRes(Res.string.concord_dissolve_title, communityName)) },
+        text = { Text(stringRes(Res.string.concord_dissolve_message)) },
+        confirmButton = {
+            TextButton(onClick = onConfirm) {
+                Text(stringRes(Res.string.concord_dissolve_confirm), color = MaterialTheme.colorScheme.error)
+            }
+        },
+        dismissButton = {
+            TextButton(onClick = onDismiss) {
+                Text(stringRes(Res.string.cancel))
+            }
+        },
+    )
+}
+
 /** A pending channel create ([channelIdHex] null) or rename target. */
 private data class ConcordChannelEditor(
     val channelIdHex: String?,

commonsUI/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/viewmodels/AccountViewModel.kt

@@ -78,6 +78,8 @@ import com.vitorpamplona.amethyst.commons.resources.cashu_successful_redemption_
 import com.vitorpamplona.amethyst.commons.resources.concord_channel_rotate_key
 import com.vitorpamplona.amethyst.commons.resources.concord_channel_rotate_key_done
 import com.vitorpamplona.amethyst.commons.resources.concord_channel_rotate_key_failed
+import com.vitorpamplona.amethyst.commons.resources.concord_dissolve_community
+import com.vitorpamplona.amethyst.commons.resources.concord_dissolve_failed
 import com.vitorpamplona.amethyst.commons.resources.concord_kicked_message
 import com.vitorpamplona.amethyst.commons.resources.concord_kicked_message_unnamed
 import com.vitorpamplona.amethyst.commons.resources.concord_kicked_title
@@ -652,6 +654,14 @@ class AccountViewModel(
         toastManager.toast(Res.string.concord_pin_failed_title, message)
     }
 
+    /** Dissolve [communityId] for good (CORD-02 §9, owner only); a refusal surfaces as a toast. */
+    fun dissolveConcordCommunity(communityId: String) =
+        launchSigner {
+            if (!account.concord.dissolveConcordCommunity(communityId)) {
+                toastManager.toast(Res.string.concord_dissolve_community, Res.string.concord_dissolve_failed)
+            }
+        }
+
     /**
      * Rotate Private Channel [channelIdHex]'s key (CORD-06). The rotation publishes a chunk per
      * member and can take a while, so both outcomes are toasted: a silent menu item left the