feat(telegram): display tool execution status messages

Telegram bot now shows tool status during execution:
- Sends status message when tool starts (tool name + args snippet)
- Edits status message with result on completion
- Keeps typing indicator active during tool execution
- Adds setOnToolUse() to NativeAgent for per-message callback control

src/backends/native/agent.ts

@@ -190,4 +190,8 @@ export class NativeAgent {
   getModelTier(): ModelTier {
     return this.currentTier;
   }
+
+  setOnToolUse(callback: ((event: ToolUseEvent) => void) | undefined): void {
+    this.onToolUse = callback;
+  }
 }