fix: end handheld runs that lose their input

Start + Select now kills a sentinel the launcher owns, and the launcher
asks the interface to stop, so a running install still writes its result.
A mapper that dies, a chvt the compositor refuses, a terminal app that
cannot open and a read-only card each end the run or hand over to the
next route instead of a console waiting for a button. muOS starts
gptokeyb2 with -X and keeps muxterm off the pad so Y opens the options.

scripts/build_port.py

@@ -103,7 +103,6 @@ def archive_members(name: str, root: Path = REPO_ROOT) -> list[tuple[str, Path]]
         source = ports / "muos"
         members = [
             ("RetroBIOS/mux_launch.sh", source / "mux_launch.sh"),
-            ("RetroBIOS/muxterm.gptk", source / "muxterm.gptk"),
             ("RetroBIOS/README.md", source / "README.md"),
             *_engine("RetroBIOS", root),
         ]