原创UTF-8编码练习 / Original UTF-8 encoding exercise
两个正确CSV只差EFBBBF。姓名上海/Zoë/東京，编号0007/0008/0009，金额合计20.00。
Valid sources differ only byBOM. Preserve all three names and identifiers. Amount12.50+0+7.50=20.00.
损坏副本故意含U+FFFD，不是正确原件。
The damaged control deliberately containsU+FFFD. Re-decoding cannot infer the lost name.
Byte checks are not an Excel UI test. Current browser-tool downloads are checked separately.
