fix: harden pi maintenance lifecycle

tools/thothctl/internal/pi/durable_unix.go

@@ -0,0 +1,15 @@
+//go:build !windows
+
+package pi
+
+import "os"
+
+// durableReplace acknowledges both the data file and its directory entry. A successful return
+// is the strongest atomic replacement guarantee supported by Unix filesystems.
+func durableReplace(temporary, target, directory string) error {
+	if err := os.Rename(temporary, target); err != nil { return err }
+	dir, err := os.Open(directory)
+	if err != nil { return err }
+	defer dir.Close()
+	return dir.Sync()
+}