Record: handler feedback and integration conflicts

Outcome

Four problems from the user story were fixed.

Run once now reports “Starting {name}: process {pid}” for several seconds instead of starting silently.
Inspect now shows a full report instead of an empty box.
Integrate now shows exactly what was written.
Integrating a second version of an already-integrated application now presents choices instead of a dead-end error.

Symptom	Cause	Fix
Run once gave no feedback during a slow start	the handler replaced itself with the AppImage, so nothing was left to report	fork, `setsid`, and exec in the child; the parent shows a notice with the child process id for several seconds (`notify-send -t 5000`, else `zenity --info --timeout=5`, else standard output)
Inspect showed an empty box	`zenity --text-info` reads its body from standard input or `--filename`; the report was passed through `--text`, which is only the label	the report is rendered in-process and handed over with `--filename`
Integrate did “something” with no summary	the success dialog only named the desktop id	a scrollable report now shows the launcher, AppImage, icon, manifest, notes, warnings, launcher contents, and the list of actions
A new FreeCAD version failed with a useless error	the tool had no concept of an application that is already integrated	conflicts are detected and named, and the user is offered Replace existing, Add alongside, or Cancel

Detection matches an existing launcher against the new AppImage by normalized Name (so FreeCAD and FreeCAD (1) match), X-AppImage-Name, StartupWMClass, and the AppImage file stem.
Each conflict records its origin: this tool, AppImageLauncher (it still carries X-AppImage-Identifier), or unknown.
--replace moves each displaced launcher into $XDG_DATA_HOME/gnome-appimage-integration/backup/ and records it in the manifest; uninstall moves it back.
--add keeps the existing launcher and installs under a suffixed desktop file id such as org.example.Probe-2.desktop.
A launcher this tool already owns at the same desktop id is treated as an in-place upgrade, not a conflict; its old manifest is retired so list does not show a stale entry.
The failure message names each conflicting launcher and states both choices.

Observed 2026-09-22 on this host, read-only.

The new download was $HOME/Downloads/FreeCAD_1.1.3-Linux-x86_64-py311.AppImage, not executable, so a right-click offers the handler.
FreeCAD 1.1.1 had been integrated by this tool: manifest 84b4aad2fb518980, launcher org.freecad.FreeCAD.desktop.
The AppImageLauncher-era launcher appimagekit_f55dc857fd6b44ae58db0c1e87cf797c-FreeCAD.desktop was still present.
appimage-integrate plan on the new download now reports one conflicting launcher, names it as AppImageLauncher, and offers --replace and --add.
The upgrade was deliberately left for the owner to choose:
- appimage-integrate install --replace "$HOME/Downloads/FreeCAD_1.1.3-Linux-x86_64-py311.AppImage"
- appimage-integrate install --add "$HOME/Downloads/FreeCAD_1.1.3-Linux-x86_64-py311.AppImage"

Verified 2026-09-22 with make test; all fourteen test scripts passed.

tests/90-integration-conflicts.sh is new and covers: a refusing plan that names the conflict and both choices, --replace backing up the displaced launcher, uninstall restoring it, --add creating org.example.Probe-2.desktop, and explain showing the embedded entry.
tests/70-integration-sandbox.sh now also covers run --detached reporting the start and the process id.
The real files were only read; plan and explain were run without changing anything.

080334e feat: give the handler feedback and offer choices on integration conflicts