minimax-xlsx: scripts crash with UnicodeEncodeError on Windows when output is piped

Summary

Every script in skills/minimax-xlsx/scripts/ prints non-ASCII characters (✓, →, —, ─). On Windows, Python uses the legacy ANSI codepage (e.g. cp1252) for piped stdout — and piped is how agent shells capture output, and how any scripted/CI invocation runs — so the first such print raises UnicodeEncodeError and the script dies mid-operation.

Real-world failure

Hit during an offline install verification on Windows 10, Python 3.14 (python-3.14.6-amd64.exe, default locale en-US/cp1252):

File "...\minimax-xlsx\scripts\\\xlsx_pack.py", line 65, in pack
    print("✓ All XML files are well-formed")
File "C:\Program Files\Python314\Lib\encodings\cp1252.py", line 19, in encode
    return codecs.charmap_encode(input,self.errors,encoding_table)[0]
UnicodeEncodeError: 'charmap' codec can't encode character '\u2713' in position 0: character maps to <undefined>

The pack itself had succeeded — the crash is purely in the progress output, but it exits non-zero and aborts whatever invoked it. Note the same crash hits agent runtime use of the skill on Windows, not just installers: agent tools capture script output through pipes.

Reproduction (any OS)

PYTHONIOENCODING=cp1252 python3 skills/minimax-xlsx/scripts/xlsx_pack.py \
  skills/minimax-xlsx/templates/minimal_xlsx /tmp/test.xlsx | cat
# → UnicodeEncodeError: 'charmap' codec can't encode character '\u2713'

Affected (all print non-ASCII): xlsx_pack.py, xlsx_unpack.py, xlsx_reader.py, formula_check.py, xlsx_add_column.py, xlsx_insert_row.py, xlsx_shift_rows.py, shared_strings_builder.py, style_audit.py, libreoffice_recalc.py.

Proposed fix

Reconfigure stdout/stderr with errors="replace" at startup so output degrades to ? instead of crashing — no behavior change on UTF-8 terminals, and the scripts' exit codes / file outputs are untouched. PR incoming.