mapsize 1.2.0: permanent delete and in-map reveal when headless

On a headless Linux or BSD system (no DISPLAY or WAYLAND_DISPLAY) nothing
empties the freedesktop trash, so trashing never freed space. There, d now
deletes permanently after an explicit confirmation, checking owner and type
against the scan and removing through an os.Root on the parent so a swapped
symlink cannot redirect it. o shows the folder in the map instead of
launching a file manager. Desktop sessions, macOS and Windows are unchanged.

internal/platform/ops_darwin.go

@@ -75,3 +75,7 @@ func volumeOf(path string) string {
 	}
 	return ""
 }
+
+// Headless is always false: macOS has Finder and the Trash even without
+// $DISPLAY (which it does not use).
+func Headless() bool { return false }