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_linux.go

@@ -123,3 +123,10 @@ func mountTop(path string, dev uint64) string {
 		cur = parent
 	}
 }
+
+// Headless reports whether there is no graphical session (no X or Wayland
+// display), so there is no file manager to open and no desktop trash anyone
+// will empty.
+func Headless() bool {
+	return os.Getenv("DISPLAY") == "" && os.Getenv("WAYLAND_DISPLAY") == ""
+}