fix: restore Windows CI for v0.7.1

[atomize-lab]

Summary

• make the live demo's terminal output portable on legacy Windows console encodings;
• use explicit UTF-8 for demo JSON file I/O;
• add a regression test that runs the demo with PYTHONIOENCODING=cp1252;
• prepare the v0.7.1 maintenance release notes.

Root cause

The demo introduced Unicode box-drawing and status glyphs after v0.7.0. On a Windows cp1252 console, the first glyph raised UnicodeEncodeError, which made only the Windows pytest matrix fail.

Validation

• RED: the new cp1252 regression test failed on the original code with UnicodeEncodeError;
• GREEN: 220 tests passed on Python 3.12.3;
• GREEN: 220 tests passed on Python 3.13.14;
• python tools/citeseal.py lint passed with pyflakes;
• compileall, git diff --check, and a direct cp1252 demo smoke test passed.

All commits are authored and committed by champ <champ@users.noreply.github.com>.