fix(minimax-xlsx): scripts crash printing ✓/→ through non-UTF8 Windows pipes

[quickbeard]

Fixes #110.

Problem

Every script in skills/minimax-xlsx/scripts/ prints non-ASCII characters (✓, →, —, ─). On Windows, Python encodes piped stdout with the legacy ANSI codepage (e.g. cp1252), which cannot represent them — the first such print raises UnicodeEncodeError and kills the script mid-operation, even though the underlying work (packing, validation, …) succeeded. Piped output is the common case: agent shells capture script output through pipes, as do installers and CI.

Observed in the wild on Windows 10 / Python 3.14 during an offline install verification (full traceback in #110); reproducible on any OS with:

PYTHONIOENCODING=cp1252 python3 skills/minimax-xlsx/scripts/xlsx_pack.py \
  skills/minimax-xlsx/templates/minimal_xlsx /tmp/test.xlsx | cat

Fix

Add a small startup snippet to each of the ten scripts, right after the import block:

for _stream in (sys.stdout, sys.stderr):
    try:
        _stream.reconfigure(errors="replace")
    except (AttributeError, ValueError):
        pass

Unencodable characters degrade to ? instead of crashing. On UTF-8 terminals (all of Linux/macOS, and Windows consoles) output is byte-identical to before; exit codes and file outputs are untouched everywhere. The try/except keeps the scripts safe under detached/wrapped streams.

Verified: the repro above crashes before this change and completes with exit 0 after (the ✓ renders as ? under cp1252, verbatim under UTF-8). All ten scripts still compile (python -m py_compile).

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