fix(chats): stop crashing when a relay's group directory is sorted

Browsing a relay's groups (Relay Groups → Find groups → pick a relay)
crashed the app to the launcher:

    java.lang.IllegalArgumentException: Comparison method violates its
    general contract!
      at java.util.TimSort.mergeLo
      ...
      at RelayGroupChannelListScreen$allChannels$3$1$1.emit

`sortedBy { it.toBestDisplayName().lowercase() }` re-evaluates its key on
every comparison, and the key comes from mutable shared state — the
channel's display name, which a kind-39000 directory event can change
while the sort is running. TimSort detects the inconsistency and throws.

The failure scales with directory size and needs no user action: a relay
hosting 1237 groups tripped it on the first browse, while a relay with 18
never did — which is why an earlier sweep of this same screen missed it.
v1.12.6 already fixed this class elsewhere ("snapshot live-stream status
order before sorting"); these sites were not covered.

Adds `sortedBySnapshot`, which computes each key ONCE before any
comparison runs, and applies it to all four sites that sorted live
objects by their display name: the relay group directory (both the
initial value and the observer), the parent-group picker, and the
name-ordered search results. The picker's site also had to materialise
its Sequence first, since sorting lazily would have re-introduced the
same window.

Verified on device: the exact tap that crashed now loads the screen with
zero FATAL EXCEPTIONs and the app stays in the foreground.

Found while setting up a NIP-29 group to test the admin surface, which is
also how the directory got large enough to expose it.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/publicChannels/relayGroup/RelayGroupChannelListScreen.kt

@@ -53,6 +53,7 @@ import com.vitorpamplona.amethyst.R
 import com.vitorpamplona.amethyst.commons.icons.symbols.Icon
 import com.vitorpamplona.amethyst.commons.icons.symbols.MaterialSymbols
 import com.vitorpamplona.amethyst.commons.model.nip29RelayGroups.RelayGroupChannel
+import com.vitorpamplona.amethyst.commons.util.sortedBySnapshot
 import com.vitorpamplona.amethyst.model.LocalCache
 import com.vitorpamplona.amethyst.model.nip11RelayInfo.isRelaySignedRelayGroup
 import com.vitorpamplona.amethyst.model.nip11RelayInfo.loadRelayInfo
@@ -101,13 +102,13 @@ fun RelayGroupChannelListScreen(
     // updates as directory events arrive with no polling. The initial value is sorted too
     // so the first frame doesn't reshuffle when the first emission arrives.
     val allChannels by produceState(
-        initialValue = accountViewModel.getRelayGroupChannelsOnRelay(relay).sortedBy { it.toBestDisplayName().lowercase() },
+        initialValue = accountViewModel.getRelayGroupChannelsOnRelay(relay).sortedBySnapshot { it.toBestDisplayName().lowercase() },
         relay,
     ) {
         LocalCache
             .observeEvents<GroupMetadataEvent>(Filter(kinds = listOf(GroupMetadataEvent.KIND)))
             .collect {
-                value = accountViewModel.getRelayGroupChannelsOnRelay(relay).sortedBy { it.toBestDisplayName().lowercase() }
+                value = accountViewModel.getRelayGroupChannelsOnRelay(relay).sortedBySnapshot { it.toBestDisplayName().lowercase() }
             }
     }
 

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/publicChannels/relayGroup/RelayGroupParentPicker.kt

@@ -65,6 +65,7 @@ import com.vitorpamplona.amethyst.R
 import com.vitorpamplona.amethyst.commons.icons.symbols.Icon
 import com.vitorpamplona.amethyst.commons.icons.symbols.MaterialSymbols
 import com.vitorpamplona.amethyst.commons.model.nip29RelayGroups.RelayGroupChannel
+import com.vitorpamplona.amethyst.commons.util.sortedBySnapshot
 import com.vitorpamplona.amethyst.model.LocalCache
 import com.vitorpamplona.amethyst.model.nip11RelayInfo.isRelaySignedRelayGroup
 import com.vitorpamplona.amethyst.model.nip11RelayInfo.loadRelayInfo
@@ -467,8 +468,8 @@ private fun pickCandidates(
         .asSequence()
         .filter { it.groupId.id !in forbidden }
         .filter { it.event != null && isRelaySignedRelayGroup(it, relayInfo) }
-        .sortedBy { it.toBestDisplayName().lowercase() }
         .toList()
+        .sortedBySnapshot { it.toBestDisplayName().lowercase() }
 
 /**
  * The set of group ids reachable as descendants of [rootId] on [relay], following each group's

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/search/SearchResultSorter.kt

@@ -21,6 +21,7 @@
 package com.vitorpamplona.amethyst.commons.search
 
 import com.vitorpamplona.amethyst.commons.model.User
+import com.vitorpamplona.amethyst.commons.util.sortedBySnapshot
 import com.vitorpamplona.quartz.nip01Core.core.Event
 import com.vitorpamplona.quartz.nip23LongContent.LongTextNoteEvent
 import com.vitorpamplona.quartz.utils.currentTimeSeconds
@@ -64,7 +65,7 @@ object SearchResultSorter {
         order: SearchSortOrder,
     ): List<User> =
         when (order) {
-            SearchSortOrder.NAME_AZ -> people.sortedBy { it.toBestDisplayName().lowercase() }
+            SearchSortOrder.NAME_AZ -> people.sortedBySnapshot { it.toBestDisplayName().lowercase() }
             SearchSortOrder.NAME_ZA -> people.sortedByDescending { it.toBestDisplayName().lowercase() }
             else -> people
         }

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/util/SortedBySnapshot.kt

@@ -0,0 +1,39 @@
+/*
+ * 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.amethyst.commons.util
+
+/**
+ * Sorts by a key computed ONCE per element, before any comparison runs.
+ *
+ * `sortedBy { it.liveProperty }` re-evaluates the key on every comparison, which is a crash — not a
+ * cosmetic issue — when the key comes from mutable shared state such as a User's or channel's display
+ * name. A relay event landing mid-sort changes the key underneath TimSort, it detects the
+ * inconsistency, and throws `IllegalArgumentException: Comparison method violates its general
+ * contract!`. It needs no user action and scales with list size: a directory of a thousand groups
+ * trips it readily while a handful never does.
+ *
+ * Snapshotting first makes the comparator total and stable for the duration of the sort, whatever the
+ * network does. The extra list is the price of not crashing.
+ */
+inline fun <T, R : Comparable<R>> Iterable<T>.sortedBySnapshot(key: (T) -> R): List<T> =
+    map { it to key(it) }
+        .sortedBy { it.second }
+        .map { it.first }