Clean up documentation redundancy:
- Delete docs/Archiv_fertig_-_Check_und_Installation.md: an AI hand-off
transcript (first-person, stale test count, malformed markdown) whose
useful content is already in INSTALL_FROM_ARCHIVE.md.
- Delete docs/How_to_use.md after moving its one unique asset -- the
old-script -> new-command migration table -- into the README; drop it
from the build_archive manifest.
- Fix INSTALL_FROM_ARCHIVE.md drift: list LICENSE/CHANGELOG.md in the
archive allowlist and use `python -m pytest`.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>