Every port box was parseInt(e.target.value) || <default>. Delete the contents
and parseInt gives NaN, so the default is written straight back: the digits
reappear under the cursor and the only way to enter a different port is to
overwrite it character by character. Reported on the cluster editor; the same
line existed in eight other places.
One PortInput component now holds the raw TEXT as its state and only tells the
parent about a value that is actually a port. An empty box stays empty while you
type; on blur an invalid one falls back to the default, so nothing is ever saved
as 0 or NaN. It adopts a value arriving from the backend only while the operator
has not started typing — re-syncing mid-edit is the behaviour being fixed.
This is the controlled-input trap the project notes already warn about: keep the
raw text in local state and derive the stored value from it.