refactor: remove direct stdout handling in spinner class

- Eliminated the `_raw_write` function to simplify output handling in the `KawaiiSpinner` class.
- Updated spinner animation and final message display to use standard print statements, ensuring compatibility with prompt_toolkit.
- Improved code clarity and maintainability by reducing complexity in the output rendering process.

agent/display.py

@@ -7,7 +7,6 @@ Used by AIAgent._execute_tool_calls for CLI feedback.
 import json
 import os
 import random
-import sys
 import threading
 import time
 
@@ -16,22 +15,6 @@ _RED = "\033[31m"
 _RESET = "\033[0m"
 
 
-def _raw_write(text: str):
-    """Write directly to the real stdout, bypassing prompt_toolkit's patch_stdout proxy.
-
-    prompt_toolkit's StdoutProxy intercepts sys.stdout and can swallow or
-    mishandle \\r carriage returns and inline ANSI escapes that the spinner
-    relies on.  sys.__stdout__ is the original file object before any monkey
-    patching, so writes go straight to the terminal.
-    """
-    out = sys.__stdout__
-    try:
-        out.write(text)
-        out.flush()
-    except (ValueError, OSError):
-        pass
-
-
 # =========================================================================
 # Tool preview (one-line summary of a tool call's primary argument)
 # =========================================================================
@@ -186,10 +169,8 @@ class KawaiiSpinner:
             frame = self.spinner_frames[self.frame_idx % len(self.spinner_frames)]
             elapsed = time.time() - self.start_time
             line = f"  {frame} {self.message} ({elapsed:.1f}s)"
-            # \033[2K erases the entire current line, \r moves cursor to col 0.
-            # Using _raw_write bypasses patch_stdout so the animation renders
-            # even when prompt_toolkit owns the terminal.
-            _raw_write(f"\033[2K\r{line}")
+            clear = '\r' + ' ' * self.last_line_len + '\r'
+            print(clear + line, end='', flush=True)
             self.last_line_len = len(line)
             self.frame_idx += 1
             time.sleep(0.12)
@@ -209,9 +190,9 @@ class KawaiiSpinner:
         self.running = False
         if self.thread:
             self.thread.join(timeout=0.5)
-        _raw_write(f"\033[2K\r")
+        print('\r' + ' ' * (self.last_line_len + 5) + '\r', end='', flush=True)
         if final_message:
-            _raw_write(f"  {final_message}\n")
+            print(f"  {final_message}", flush=True)
 
     def __enter__(self):
         self.start()