Merge master: the downloadable builds

Three files disagreed. The test workflow gained a job on either side, so
both stay: the Mac now parses the release and packaging scripts as well,
and Windows keeps its own job below.

`restart` and `launch_gui` both start Dikte again, and master moved that
argv into `ipc.launcher()` because a packaged build has no `__main__.py`
to name. Windows still cannot use execv there, so the detached start it
needs now takes what the launcher hands it rather than spelling the
interpreter and the script itself.

The test counts in CONTRIBUTING are the suite as it stands after the
merge: 1104 of 1147 run anywhere, and the 43 left are the Linux ones.

.github/workflows/tests.yml

@@ -74,6 +74,9 @@ jobs:
           bash -n scripts/install-mac.sh
           bash -n scripts/update.sh
           bash -n scripts/uninstall.sh
+          bash -n scripts/release.sh
+          bash -n packaging/build-appimage.sh
+          bash -n packaging/build-dmg.sh
 
   # The same job again for the same reason. The Windows backends are faked at
   # the one function that loads user32 and kernel32, so every line of them is