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/delete_unix.go

@@ -0,0 +1,35 @@
+//go:build unix
+
+package platform
+
+import (
+	"errors"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"syscall"
+)
+
+// Delete permanently removes path (recursively for a directory) if it still
+// matches want. The check and the removal both go through an os.Root on the
+// parent directory, so a symlink swapped in since the scan cannot redirect
+// the removal outside it.
+func Delete(path string, want Expect) error {
+	if err := checkAbs(path); err != nil {
+		return err
+	}
+	dir, base := filepath.Dir(path), filepath.Base(path)
+	root, err := os.OpenRoot(dir)
+	if err != nil {
+		return err
+	}
+	defer root.Close()
+	fi, err := root.Lstat(base)
+	if err != nil {
+		return err
+	}
+	if fi.Sys().(*syscall.Stat_t).Uid != want.UID || fi.Mode()&fs.ModeType != want.Mode&fs.ModeType {
+		return errors.New("item changed since the scan (owner or type differs); rescan first")
+	}
+	return root.RemoveAll(base)
+}