fix: multi byte run boundary for cut long title

[ferhatelmas]

Multi-byte rune at boundary gets corrupted:

• A string where a multi-byte character spans the 150-byte boundary
• Chinese character "中" is 3 bytes (0xE4 0xB8 0xAD)
• If we have 149 ASCII chars + "中", the "中" starts at byte 149 and ends at byte 151
• cutLongTitle should cut before "中", returning 149 bytes
• But the current implementation returns 150 bytes, cutting "中" in half and making string invalid

[LinkinStars]

Great! Thank you for your contribution. This is important to us.