Settings: HANDS_SWAP_SIDES defaults to auto, and old untouched configs move to it

frametop.conf.example said HANDS_SWAP_SIDES=0, and desktops.sh copies it on a
fresh install, so every new install forced ft-camd's side camera names and
turned the hand tracker's own side check off. Some SteamVR restarts swap those
names, and then hands land beside their cutouts and recordings are mislabelled.

The example now says auto. scripts/conf-migrate.sh, run by install.sh and
hands/rec/install.sh, replaces the old line only where it's still exactly as
the example wrote it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

hands/rec/install.sh

@@ -23,6 +23,7 @@ case ${1:-install} in
     "$root/hands/rec/build.sh"
     echo "== 4/4 ft-camd's capabilities (asks for your password) and the menu entry"
     "$root/hands/run.sh" caps
+    "$root/scripts/conf-migrate.sh"   # HANDS_SWAP_SIDES=0, the old default, becomes auto
     fill_template "$root/hands/rec/ft-handrec.desktop" |
       on_frame "mkdir -p ~/.local/share/applications && cat > $entry"
     echo