fix(discord): declare slash commands on module methods

tests/GmRelay.Bot.Tests/Discord/DiscordStartupTests.cs

@@ -1,5 +1,8 @@
 using System;
 using System.IO;
+using System.Reflection;
+using GmRelay.DiscordBot.Features.Sessions;
+using NetCord.Services.ApplicationCommands;
 
 namespace GmRelay.Bot.Tests.Discord;
 
@@ -50,6 +53,40 @@ public sealed class DiscordStartupTests
         Assert.Contains("AddModules(typeof(Program).Assembly)", program);
     }
 
+    [Theory]
+    [InlineData(typeof(DiscordNewSessionCommand), "newsession")]
+    [InlineData(typeof(DiscordListSessionsCommand), "listsessions")]
+    [InlineData(typeof(DiscordRescheduleCommand), "reschedule")]
+    public void DiscordSessionSlashCommands_ShouldBeDeclaredOnModuleMethods(Type moduleType, string commandName)
+    {
+        var executeMethod = moduleType.GetMethod("ExecuteAsync", BindingFlags.Instance | BindingFlags.Public);
+
+        Assert.NotNull(executeMethod);
+
+        var methodAttribute = Assert.Single(executeMethod.GetCustomAttributes<SlashCommandAttribute>(inherit: false));
+        var nameProperty = typeof(SlashCommandAttribute).GetProperty("Name")
+            ?? throw new InvalidOperationException("SlashCommandAttribute should expose command name.");
+
+        Assert.Equal(commandName, nameProperty.GetValue(methodAttribute));
+        Assert.Empty(moduleType.GetCustomAttributes<SlashCommandAttribute>(inherit: false));
+    }
+
+    [Fact]
+    public void DiscordSessionSlashCommands_ShouldBeDiscoverableByNetCordService()
+    {
+        var service = new ApplicationCommandService<SlashCommandContext>();
+
+        service.AddModules(typeof(DiscordNewSessionCommand).Assembly);
+
+        var commandNames = service.GetCommands()
+            .Select(command => command.Name)
+            .ToArray();
+
+        Assert.Contains("newsession", commandNames);
+        Assert.Contains("listsessions", commandNames);
+        Assert.Contains("reschedule", commandNames);
+    }
+
     [Fact]
     public void LifecycleLogger_ShouldLogGatewayLifecycleEventsWithoutTokenValues()
     {