ByteDraft encoding demos (fixtures for manual checks)

Location: crates/byte_draft/tests/fixtures/encoding_demo/

1) encoding_diff_demo_utf8.txt  ← start here
   - Open this file in ByteDraft (UTF-8).
   - Line 1 shows: Hello © € é (Unicode).
   - Save the tab (no edits), then pick ISO-8859-1 or Windows-1252 in the status bar encoding
     dropdown: the file reloads from disk and those UTF-8 bytes are reinterpreted as
     single-byte characters, so line 1 becomes mojibake. Switch back to UTF-8 to restore.

2) encoding_diff_demo.bin
   - Raw bytes (not valid UTF-8): Hello + 0xA9 + 0x80 + 0xE9 + CRLF.
   - Open… tries UTF-8 first; if that fails, the file is opened as ISO-8859-1 (every byte maps to
     a character). The status bar should show ISO-8859-1. Switch to Windows-1252 (clean tab) to
     reload: the middle byte 0x80 becomes € instead of U+0080. © and é match in both encodings.
   - Turn on View → Show line endings to see the CRLF badge.
