fix: clean up progress tracking, fix subagent summary field handling

- Use system/task_progress subtype (not top-level type) for subagent events
- Extract intermediate assistant text between tool calls as progress
- Only show SDK-generated summaries for subagent progress (skip noisy per-tool updates)
- Truncate progress messages to Discord 2000 char limit
- Remove verbose debug logging from production

src/message-turn-controller.ts

@@ -212,7 +212,10 @@ export class MessageTurnController {
     if (minutes > 0) elapsedParts.push(`${minutes}분`);
     elapsedParts.push(`${seconds}초`);
 
-    return `${TASK_STATUS_MESSAGE_PREFIX}${text}\n\n${elapsedParts.join(' ')}`;
+    const suffix = `\n\n${elapsedParts.join(' ')}`;
+    const maxText = 2000 - TASK_STATUS_MESSAGE_PREFIX.length - suffix.length;
+    const truncated = text.length > maxText ? text.slice(0, maxText - 1) + '…' : text;
+    return `${TASK_STATUS_MESSAGE_PREFIX}${truncated}${suffix}`;
   }
 
   private clearProgressTicker(): void {