fix(bundle): reset desktop entry paths and drop D-Bus activation files

[FeiLiuEM]

What & why

The AppImage ships a desktop entry whose Exec/TryExec point at the CI build directory, plus a D-Bus service file with the same path and DBusActivatable=true:

$ ./Ghostty-1.3.2-main+a4aacd9-x86_64.AppImage --appimage-extract >/dev/null
$ grep -rn '/__w/' squashfs-root/ | cut -c1-120
squashfs-root/com.mitchellh.ghostty.desktop:6:TryExec=/__w/ghostty-appimage/…
squashfs-root/share/applications/com.mitchellh.ghostty.desktop:6:TryExec=/__w/…
squashfs-root/share/dbus-1/services/com.mitchellh.ghostty.service:4:Exec=/__w/…

Cause chain:

1. Upstream dist/linux/app.desktop.in / dbus.service.in use @GHOSTTY@, which zig build substitutes with the absolute build prefix (inside CI: /__w/ghostty-appimage/ghostty-appimage/ghostty-<ver>/zig-out/bin/ghostty).
2. bundle-appimage.sh passes that generated file as DESKTOP=…; quick-sharun copies it into $APPDIR verbatim and only strips DBusActivatable.
3. bundle-appimage.sh then does cp -rf ./ghostty-<ver>/zig-out/share/* ./AppDir/share/ after quick-sharun, which re-adds the unsanitized entry (share/applications/…desktop, still DBusActivatable=true) and adds share/dbus-1/services/…service.

Integration tools that extract the embedded entry (appimaged, or a manual copy into ~/.local/share/applications/) therefore get a TryExec that cannot exist, and KDE/GNOME hide the entry or fail to launch it — the symptom in #127, which is still reproducible on the current tip build.

The change

After that cp, rewrite the absolute paths to the binary name the README documents (install ./Ghostty-*.AppImage $HOME/.local/bin/ghostty), remove DBusActivatable (quick-sharun deliberately strips it from the top level entry; the copy brought it back) and don't ship the unusable dbus-1 service file.

Verification

Ran the new block against the files extracted from the current tip AppImage (Ghostty-1.3.2-main+a4aacd9-x86_64, sha256 0ff324551791220ec4a5d41cb562e7f2b272559cfb2c4ff0288a81c911939a57):

before: TryExec=/__w/…/zig-out/bin/ghostty            after: TryExec=ghostty
        Exec=/__w/…/zig-out/bin/ghostty --gtk-…                Exec=ghostty --gtk-single-instance=true   (both entries, new-window action included)
        share/applications/…desktop: DBusActivatable=true      (line removed)
        share/dbus-1/services/…service: Exec=/__w/…            (directory removed)
desktop-file-validate: clean on both entries
shellcheck --severity=warning --shell=sh bin/bundle-appimage.sh: clean
shfmt -d -s bin/bundle-appimage.sh: no diff

I did not run the full CI build (needs the Arch container); the patch only touches files that are already in AppDir at that point, and the transformation above is exactly what runs there.

Fixes #168. Happy to follow up with a guard in repo-management.sh validate-appimage (grep -q '/__w/' on the embedded entry → fail) if you want the regression covered by CI as well.

[Samueru-sama]

dbus activation is disabled automatically by quick-sharun: https://github.com/pkgforge-dev/Anylinux-AppImages/blob/aab8d07500fb9972c8e6bb44afd92b8742dc0c92/useful-tools/quick-sharun.sh#L3537-L3539

[FeiLiuEM]

Withdrawing this: the DBus part is already handled by quick-sharun for the entry that matters, and my impact claim did not hold (see the analysis in #168). I may follow up with a minimal Exec/TryExec-only patch if the second desktop copy in the image turns out to be unintentional.