Write when the user asks, not when the focus moves

A draft that lives beside the stored value, and a commit that is a button:

// Keyed on the stored value: a change from anywhere else re-seeds the field.
var draft by remember(storedEndpoint) { mutableStateOf(storedEndpoint) }

BasicTextField(
    value = draft,
    onValueChange = { draft = it },
    /* decorationBox shows a "wss://…" placeholder while draft is empty */
)