README 'What's new in 5.1.0' + a new 'Compression comparison' section with
measured ratio/throughput tables vs zstd/gzip/lz4 and a 5.0.0->5.1.0 delta
table; fix the stale codec-internals section (2.60.4 -> 2.65.0, and the
now-wrong 'wrapper forces format_v2' paragraph). CHANGELOG 5.1.0 entry.
Bump Version: in the rpm/opensuse specs (+changelog), the homebrew formula
url/version, the guix package version, and the gui README to 5.1.0.
Adds packaging/guix/vaptvupt.scm so VaptVupt is reproducibly installable on
GNU Guix (guix package -f). The GUI launcher sets LD_LIBRARY_PATH to the Qt6
leaf libraries PySide6 needs but does not carry in its RUNPATH — libGL (mesa),
libxkbcommon, the X11/xcb family, libzstd (from zstd's "lib" output), harfbuzz,
icu, wayland, glib, dbus, ... Without them, `import PySide6.QtWidgets` fails with
"libGL.so.1 / libzstd.so.1: cannot open shared object file" and the GUI prints
"requires PySide6 or PyQt6" on Guix (which has no global /usr/lib to satisfy
them). Qt's own libraries are deliberately excluded from LD_LIBRARY_PATH so they
resolve via PySide6's RUNPATH (a second copy causes private-API symbol clashes).
Also puts python-shiboken-6's site-packages on GUIX_PYTHONPATH.
Verified: full PySide6 QtWidgets/QtGui/QtCore import + QApplication, and the
windowed GUI launches, on this Guix system.
