fix(telegram): cut the voice transcript echo to 1024 characters

hosts/Volcanic.AgenticCore.Telegram/Inbound/InboundMedia.cs

@@ -20,6 +20,9 @@ public sealed class InboundMedia(TelegramSender sender, TelegramOptions options,
     /// <summary>Sent for a voice note or audio file when no speech-to-text service is configured.</summary>
     public const string SpeechNotConfiguredNotice = "Voice messages need speech-to-text: set OPENAI_API_KEY (or Telegram:Speech:ApiKey) on the bot host.";
 
+    /// <summary>The longest <c>🎤</c> echo, in UTF-16 code units; a long transcript is cut so it doesn't flood the chat.</summary>
+    public const int MaxEchoLength = 1024;
+
     /// <summary>Sent when the transcript is empty.</summary>
     public const string NoWordsNotice = "I couldn't make out any words in that voice message.";
 
@@ -170,10 +173,20 @@ public sealed class InboundMedia(TelegramSender sender, TelegramOptions options,
             await chat.Renderer.SayAsync(NoWordsNotice).ConfigureAwait(false);
             return;
         }
-        await chat.Renderer.SayAsync("🎤 " + transcript).ConfigureAwait(false); // plain text, cut to 4096 by the sender
+        await chat.Renderer.SayAsync(Echo(transcript)).ConfigureAwait(false); // plain text
         draft.Body.Add($"[Voice message] {transcript}");
     }
 
+    /// <summary>The <c>🎤 …</c> echo, cut to <see cref="MaxEchoLength"/> characters with <c>…</c> (the model gets all of it).</summary>
+    internal static string Echo(string transcript)
+    {
+        var echo = "🎤 " + transcript;
+        if (echo.Length <= MaxEchoLength) return echo;
+        var cut = MaxEchoLength - 1;
+        if (char.IsHighSurrogate(echo[cut - 1])) cut--; // don't split an emoji
+        return echo[..cut] + "…";
+    }
+
     /// <summary>
     /// The name an audio file is sent to speech to text under: OpenAI picks the format from the extension, so it's an
     /// ASCII <c>audio.&lt;ext&gt;</c> from the original extension when OpenAI knows it, else from the MIME type.