feat(concord): add an Open channel action to the minichat thread

A Concord minichat pins its root and backfills it from the channel history, but
when the root is still loading (or you aren't a member yet) there was no way out.
Add an Open channel action to the top bar for Concord threads, navigating to the
full channel (Route.Concord) where the whole timeline loads and membership lives
— the correct affordance to click through to the chat room itself.

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

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/minichat/MinichatScreen.kt

@@ -59,6 +59,7 @@ import com.vitorpamplona.amethyst.model.Note
 import com.vitorpamplona.amethyst.service.relayClient.reqCommand.event.EventFinderFilterAssemblerSubscription
 import com.vitorpamplona.amethyst.ui.components.ThinPaddingTextField
 import com.vitorpamplona.amethyst.ui.navigation.navs.INav
+import com.vitorpamplona.amethyst.ui.navigation.routes.Route
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.feed.ChatroomMessageCompose
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.feed.LocalSuppressReplyToNoteId
@@ -146,6 +147,16 @@ fun MinichatScreen(
                         SymbolIcon(symbol = MaterialSymbols.AutoMirrored.ArrowBack, contentDescription = stringRes(R.string.back))
                     }
                 },
+                actions = {
+                    // For a Concord thread, always offer a jump to the full channel — the "chat room
+                    // itself", where the whole timeline loads and (if you aren't a member yet) you can
+                    // join. This is the way out when the pinned root is still backfilling or unavailable.
+                    if (isConcord) {
+                        IconButton(onClick = { nav.nav(Route.Concord(communityId!!, channelId!!)) }) {
+                            SymbolIcon(symbol = MaterialSymbols.Forum, contentDescription = stringRes(R.string.concord_open_channel))
+                        }
+                    }
+                },
             )
         },
     ) { padding ->

amethyst/src/main/res/values/strings.xml

@@ -313,6 +313,7 @@
     <string name="concord_channels_empty">No channels yet.</string>
     <string name="concord_show_all_channels">Show all channels</string>
     <string name="concord_send_image_title">Send image</string>
+    <string name="concord_open_channel">Open channel</string>
     <string name="concord_typing_one">%1$s is typing…</string>
     <string name="concord_typing_two">%1$s and %2$s are typing…</string>
     <string name="concord_typing_many">Several people are typing…</string>