deploy: gc jupiter after every switch (eMMC space)

configurationLimit prunes generations beyond the cap as part of the switch,
but pruning only drops a generation as a GC root — the store paths
themselves still need an actual collect to free the disk. Do that right
after every jupiter switch rather than waiting up to a week for
gc.dates=weekly to matter again.

scripts/deploy

@@ -838,6 +838,26 @@ case "$cmd" in
     else
       "${rebuild[@]}"
     fi
+
+    # jupiter's 29G eMMC has no room to just let generations pile up between
+    # gc.dates=weekly runs (common.nix) — that's exactly how it filled up
+    # once already. configurationLimit=5 (also common.nix) makes
+    # switch-to-configuration prune generations beyond 5 as part of the
+    # switch above, but pruning a generation only drops it as a GC root —
+    # the store paths themselves still need an actual collect to free the
+    # disk. So do that here, right after every switch, rather than waiting
+    # up to a week for it to matter again.
+    if [ "$cmd" = switch ] && [ "$config" = jupiter ]; then
+      echo ">> jupiter: collecting garbage post-switch (keeps the eMMC under the 5-generation cap)"
+      need ssh
+      if [ -n "$pw" ]; then
+        printf '%s\n' "$pw" | ssh "darman@$host" 'sudo -S nix-collect-garbage -d' \
+          || echo ">> warning: post-switch gc on jupiter failed — check disk space by hand" >&2
+      else
+        ssh -t "darman@$host" 'sudo nix-collect-garbage -d' \
+          || echo ">> warning: post-switch gc on jupiter failed — check disk space by hand" >&2
+      fi
+    fi
     unset pw
     ;;