fix: prune unused binary from each AppDir before linuxdeploy bundling

Previously cmake --install populated both AppDirs with both binaries,
causing the batch AppImage (57MB) to be larger than the GUI AppImage
(47MB). Add rm lines after the sanity-check block to strip the
unwanted binary from each AppDir before linuxdeploy runs.

Also prune the upstream GUI desktop files from the batch AppDir (they
reference Exec=glabels-qt which is now absent) and supply --icon-file
+ --icon-filename so --create-desktop-file resolves the icon lookup.
Both AppImages now contain only their respective binary (~33-34MB each).

Also document the QMAKE=/usr/bin/qmake6 workaround (Debian 13 Qt6
qmake discovery failure in linuxdeploy-plugin-qt).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/build-appimages.sh

@@ -34,8 +34,9 @@ PATH="$PLUGIN_DIR:$PATH"
 PLUGIN_LINK="$PLUGIN_DIR/linuxdeploy-plugin-qt"
 ln -sf "$LINUXDEPLOY_PLUGIN_QT_BIN" "$PLUGIN_LINK"
 chmod +x "$PLUGIN_LINK"
-# On Debian 13 / Qt6, the qmake symlink may resolve via qtchooser to qt5.
-# Force the plugin to use the Qt6 qmake directly.
+# Debian 13 has Qt6 only; linuxdeploy-plugin-qt's default qmake lookup looks
+# for `qmake` (Qt5 era) or `/usr/lib/qt5/bin/qmake` (neither exists). Force it
+# to the Qt6 binary explicitly so plugin staging works.
 export QMAKE=/usr/bin/qmake6
 
 echo "==> [2/6] Out-of-tree cmake build (install prefix /usr)"
@@ -58,6 +59,16 @@ DESTDIR="$APPDIR_BATCH" cmake --install "$BUILD_DIR"
 test -x "$APPDIR_GUI/usr/bin/glabels-qt" || { echo "ERROR: GUI binary missing in AppDir-gui" >&2; exit 1; }
 test -x "$APPDIR_BATCH/usr/bin/glabels-batch-qt" || { echo "ERROR: batch binary missing in AppDir-batch" >&2; exit 1; }
 
+# Prune the unwanted binary from each AppDir so linuxdeploy bundles only the
+# libs needed by the remaining binary (otherwise both AppImages carry both
+# binaries; spec §5.3 step 3 implies "AppDir-batch" should be batch-only).
+rm "$APPDIR_GUI/usr/bin/glabels-batch-qt"
+rm "$APPDIR_BATCH/usr/bin/glabels-qt"
+# Also prune the GUI desktop files from the batch AppDir: linuxdeploy's
+# --create-desktop-file doesn't suppress pre-existing desktop files, and
+# the upstream desktop files reference Exec=glabels-qt (now pruned).
+find "$APPDIR_BATCH/usr/share/applications" -name '*.desktop' -delete
+
 echo "==> [4/6] Bundle GUI AppImage"
 DESKTOP_FILE="$APPDIR_GUI/usr/share/applications/glabels-qt.desktop"
 ICON_FILE="$APPDIR_GUI/usr/share/icons/hicolor/scalable/apps/glabels.svg"
@@ -92,13 +103,17 @@ chmod +x "$GUI_OUT"
 cd "$REPO_ROOT"
 
 echo "==> [5/6] Bundle batch AppImage"
-# Batch doesn't need a desktop file or icon (CLI only).
+# Batch is CLI-only; reuse the upstream SVG icon so --create-desktop-file has
+# an icon to reference (linuxdeploy errors if the Icon= entry has no match).
+BATCH_ICON_FILE="$APPDIR_BATCH/usr/share/icons/hicolor/scalable/apps/glabels.svg"
 cd "$BUILD_DIR"
 APPIMAGE_EXTRACT_AND_RUN=1 \
 "$LINUXDEPLOY_BIN" \
   --appdir "$APPDIR_BATCH" \
   --plugin qt \
   --executable "$APPDIR_BATCH/usr/bin/glabels-batch-qt" \
+  --icon-file "$BATCH_ICON_FILE" \
+  --icon-filename glabels-batch-qt \
   --create-desktop-file \
   --output appimage