Fixes Chinese and Japanese character display corruption on Windows platform

[seii-saintway]

Issue #13

When typing Chinese or Japanese characters in Session Manager on Windows, the characters display as garbled text (e.g., "中文" appears as "荳ｭ譁"). This issue doesn't occur on Ubuntu/Linux platforms.

Description of changes:

This PR fixes UTF-8 encoding issues that cause Chinese and Japanese characters to display as garbled text on Windows platform.

• Replace windows.WriteFile with fmt.Fprint for consistent UTF-8 output display
• Ensures Windows version handles UTF-8 the same way as Unix version

Problem:

• Windows version used windows.WriteFile API for output, which doesn't handle UTF-8 properly
• Chinese/Japanese input displayed as corrupted characters (e.g., "中文" showed as "荳ｭ譁")

Solution:

• Output fix: Replace windows.WriteFile with fmt.Fprint in sessionutil_windows.go to match Unix behavior and ensure proper UTF-8 handling

Testing:

• Verified Chinese and Japanese characters now display correctly on Windows
• No impact on Unix/Linux platforms (they continue to work as before)
• Maintains backward compatibility for ASCII characters

This change aligns Windows UTF-8 handling with the Unix implementation, ensuring consistent behavior across platforms.

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