refactor: extract remaining Telegram handlers to platform-neutral contracts

- Extract CreateSessionHandler, ListSessionsHandler, DeleteSessionHandler,
  ExportCalendarHandler, HandleRescheduleTimeInputHandler,
  HandleRescheduleVoteHandler to GmRelay.Shared
- Add IPlatformMessenger methods: SendScheduleAsync, UpdateScheduleAsync,
  SendGroupMessageAsync with actions, CreateThreadAsync, DeleteThreadAsync
- Rewrite Telegram Bot wrappers as thin adapters delegating to shared handlers
- Rewrite DiscordRescheduleVoteHandler to use shared HandleRescheduleVoteHandler
- Update UpdateRouter with explicit type aliases for ambiguous handler names
- Add contract and source-inspection tests for extracted handlers
- Bump version 3.1.1 → 3.2.0

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/GmRelay.Bot/Infrastructure/Telegram/TelegramPlatformMessenger.cs

@@ -95,6 +95,68 @@ public sealed class TelegramPlatformMessenger(
             cancellationToken: ct);
     }
 
+    public async Task SendGroupMessageAsync(PlatformGroup group, string htmlText, IReadOnlyList<PlatformMessageAction> actions, CancellationToken ct)
+    {
+        EnsureTelegram(group.Platform);
+        await bot.SendMessage(
+            chatId: ParseLong(group.ExternalGroupId),
+            messageThreadId: ParseNullableInt(group.ExternalThreadId),
+            text: htmlText,
+            parseMode: ParseMode.Html,
+            replyMarkup: BuildActionsMarkup(actions),
+            cancellationToken: ct);
+    }
+
+    public async Task UpdateGroupMessageAsync(PlatformMessageRef messageRef, string htmlText, IReadOnlyList<PlatformMessageAction> actions, CancellationToken ct)
+    {
+        EnsureTelegram(messageRef.Platform);
+        await bot.EditMessageText(
+            chatId: ParseLong(messageRef.ExternalGroupId),
+            messageId: ParseInt(messageRef.ExternalMessageId),
+            text: htmlText,
+            parseMode: ParseMode.Html,
+            replyMarkup: BuildActionsMarkup(actions),
+            cancellationToken: ct);
+    }
+
+    public async Task<PlatformMessageRef> CreateThreadAsync(PlatformGroup group, string title, CancellationToken ct)
+    {
+        EnsureTelegram(group.Platform);
+        var topic = await bot.CreateForumTopic(
+            chatId: ParseLong(group.ExternalGroupId),
+            name: title,
+            cancellationToken: ct);
+
+        return new PlatformMessageRef(
+            PlatformKind.Telegram,
+            group.ExternalGroupId,
+            topic.MessageThreadId.ToString(CultureInfo.InvariantCulture),
+            string.Empty);
+    }
+
+    public Task DeleteThreadAsync(PlatformGroup group, CancellationToken ct)
+    {
+        EnsureTelegram(group.Platform);
+        if (string.IsNullOrWhiteSpace(group.ExternalThreadId))
+        {
+            return Task.CompletedTask;
+        }
+
+        return bot.DeleteForumTopic(
+            ParseLong(group.ExternalGroupId),
+            ParseInt(group.ExternalThreadId),
+            cancellationToken: ct);
+    }
+
+    public Task DeleteMessageAsync(PlatformMessageRef messageRef, CancellationToken ct)
+    {
+        EnsureTelegram(messageRef.Platform);
+        return bot.DeleteMessage(
+            ParseLong(messageRef.ExternalGroupId),
+            ParseInt(messageRef.ExternalMessageId),
+            cancellationToken: ct);
+    }
+
     public Task SendPrivateMessageAsync(PlatformPrivateMessage message, CancellationToken ct)
     {
         EnsureTelegram(message.Recipient.Platform);

src/GmRelay.Bot/Infrastructure/Telegram/UpdateRouter.cs

@@ -5,6 +5,9 @@ using GmRelay.Shared.Features.Sessions.CreateSession;
 using GmRelay.Shared.Rendering;
 using GmRelay.Bot.Features.Sessions.CreateSession;
 using GmRelay.Bot.Features.Sessions.ListSessions;
+using BotCreateSessionHandler = GmRelay.Bot.Features.Sessions.CreateSession.CreateSessionHandler;
+using BotRescheduleTimeInputHandler = GmRelay.Bot.Features.Sessions.RescheduleSession.HandleRescheduleTimeInputHandler;
+using BotRescheduleVoteHandler = GmRelay.Bot.Features.Sessions.RescheduleSession.HandleRescheduleVoteHandler;
 using GmRelay.Bot.Features.Sessions.ExportCalendar;
 using GmRelay.Bot.Features.Sessions.RescheduleSession;
 using Telegram.Bot;
@@ -20,7 +23,7 @@ namespace GmRelay.Bot.Infrastructure.Telegram;
 /// </summary>
 public sealed class UpdateRouter(
     HandleRsvpHandler rsvpHandler,
-    CreateSessionHandler createSessionHandler,
+    BotCreateSessionHandler createSessionHandler,
     JoinSessionHandler joinSessionHandler,
     LeaveSessionHandler leaveSessionHandler,
     PromoteWaitlistedPlayerHandler promoteWaitlistedPlayerHandler,
@@ -29,8 +32,8 @@ public sealed class UpdateRouter(
     ListSessionsHandler listSessionsHandler,
     ExportCalendarHandler exportCalendarHandler,
     InitiateRescheduleHandler initiateRescheduleHandler,
-    HandleRescheduleTimeInputHandler rescheduleTimeInputHandler,
-    HandleRescheduleVoteHandler rescheduleVoteHandler,
+    BotRescheduleTimeInputHandler rescheduleTimeInputHandler,
+    BotRescheduleVoteHandler rescheduleVoteHandler,
     ITelegramBotClient bot,
     IConfiguration configuration,
     ILogger<UpdateRouter> logger) : ITelegramUpdateHandler