Ports the three sections the tab was missing, against the Slint
implementation rather than invented: the section rails, the cards, and the
mix landing page with its navigation seam so back/forward behave.
The mixes reuse the shared crates for their requests -- the Slint app
already makes them, so nothing new talks to Qobuz here.
Also carries the qt-run.sh portability work needed for the Mac mini:
`free`, `nproc`, `pgrep` and `timeout` all differ or are simply absent on
BSD/macOS. Two of those bit during the first Mac build. `pgrep` exits 1
when it matches nothing -- the normal case -- and under `pipefail` that
killed the script before a single line of output, which reads exactly like
a build that did nothing. And `timeout` does not exist on macOS at all, so
the smoke produced a one-line log over which the grep cheerfully reported
"0 QML complaints": a test that never ran, rendering as a pass. The smoke
now fails outright on a log that short.
cc
vicrodh
0c159c141c