feat(e2e): #147 group creation and bot invitation scenario

- Add GroupSetupScenario: create supergroup, invite GmRelay bot, send /start,
  wait for reply, then delete the group
- Extend TelegramUserClient with DeleteGroupAsync and channel cache
- Update Program.cs to run the scenario with cleanup in finally
- Update README status table and runner documentation

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

tests/e2e/runner/TelegramUserClient.cs

@@ -1,3 +1,4 @@
+using System.Collections.Concurrent;
 using TL;
 using WTelegram;
 
@@ -7,6 +8,7 @@ public sealed class TelegramUserClient : IDisposable
 {
     private readonly Client _client;
     private readonly RunnerConfig _config;
+    private readonly ConcurrentDictionary<long, Channel> _knownChannels = new();
 
     public TelegramUserClient(RunnerConfig config)
     {
@@ -22,11 +24,11 @@ public sealed class TelegramUserClient : IDisposable
 
     public async Task<ChatGroup> CreateGroupAsync(string title, string about = "", CancellationToken cancellationToken = default)
     {
-        // Creating a megagroup gives us an UpdatesBase with Chats immediately.
         var updates = await _client.Channels_CreateChannel(title, about, megagroup: true);
         var channel = updates.Chats.Values.OfType<Channel>().FirstOrDefault()
                       ?? throw new InvalidOperationException("Failed to create a supergroup.");
 
+        _knownChannels[channel.id] = channel;
         return new ChatGroup(channel.id, channel.title);
     }
 
@@ -44,6 +46,13 @@ public sealed class TelegramUserClient : IDisposable
         await _client.Channels_InviteToChannel(channel, new InputUserBase[] { inputUser });
     }
 
+    public async Task DeleteGroupAsync(ChatGroup group, CancellationToken cancellationToken = default)
+    {
+        var channel = await ResolveChannelAsync(group.Id, cancellationToken);
+        await _client.Channels_DeleteChannel(channel);
+        _knownChannels.TryRemove(group.Id, out _);
+    }
+
     public async Task SendMessageAsync(ChatGroup group, string text, CancellationToken cancellationToken = default)
     {
         var channel = await ResolveChannelAsync(group.Id, cancellationToken);
@@ -102,12 +111,19 @@ public sealed class TelegramUserClient : IDisposable
 
     private async Task<Channel> ResolveChannelAsync(long channelId, CancellationToken cancellationToken = default)
     {
+        if (_knownChannels.TryGetValue(channelId, out var cached))
+            return cached;
+
         var dialogs = await _client.Messages_GetAllDialogs();
         var channel = dialogs.chats.Values
             .OfType<Channel>()
             .FirstOrDefault(c => c.id == channelId);
 
-        return channel ?? throw new InvalidOperationException($"Could not resolve channel {channelId}.");
+        if (channel is null)
+            throw new InvalidOperationException($"Could not resolve channel {channelId}.");
+
+        _knownChannels[channelId] = channel;
+        return channel;
     }
 }