Linux launcher runtime proof
Commit: 97cfc07759fed2a67edef22de4370ed74ff40030
Environment: linux/x64, Node v26.12.1
Production main(); real subprocesses; synthetic runtime and manager shims.
No live service or user data used.

=== control ===
Manager unit: $HOME/.config/systemd/user/t3code.service
Service XDG_CONFIG_HOME: $HOME/.config
Committed update: 1.2.3 -> 1.2.4
BEFORE: ExecStart=$FIXTURE/control/home/.t3/runtime/versions/1.2.3/t3 __service-launcher
$ node launch.mjs  # imports production launcher main()
runtime 1.2.4: received serve; exiting fixture child
Launcher completion: Active child exited unexpectedly (0).
Manager calls:
systemctl --user daemon-reload
AFTER: ExecStart=$FIXTURE/control/home/.t3/runtime/versions/1.2.4/t3 __service-launcher
unit repointed=true; daemon-reload calls=1

=== service-xdg-override ===
Manager unit: $HOME/.config/systemd/user/t3code.service
Service XDG_CONFIG_HOME: $HOME/service-config
Committed update: 1.2.3 -> 1.2.4
BEFORE: ExecStart=$FIXTURE/service-xdg-override/home/.t3/runtime/versions/1.2.3/t3 __service-launcher
$ node launch.mjs  # imports production launcher main()
runtime 1.2.4: received serve; exiting fixture child
Launcher completion: Active child exited unexpectedly (0).
[service-launcher] Could not point $FIXTURE/service-xdg-override/home/service-config/systemd/user/t3code.service at t3@1.2.4: ENOENT: no such file or directory, open '$FIXTURE/service-xdg-override/home/service-config/systemd/user/t3code.service'
Manager calls:
(none)
AFTER: ExecStart=$FIXTURE/service-xdg-override/home/.t3/runtime/versions/1.2.3/t3 __service-launcher
unit repointed=false; daemon-reload calls=0