feat(ui): type the namespace when the cluster does not list them (#84)

Some users cannot list namespaces on a cluster. The add wizard showed
an error and offered no way forward.

The namespace step now switches to a text prompt when the list call
fails or returns nothing. The prompt shows the reason and checks that
the name is a valid DNS label. Esc from a later step returns to the
prompt.

The j and k keys now type into text fields. They moved the list cursor
before, so a name such as kube-system could not be typed.

Closes #66

internal/ui/wizard_state.go

@@ -111,6 +111,7 @@ func (r ResourceType) Description() string {
 // AddWizardState maintains the state for the add port forward wizard
 type AddWizardState struct {
 	error                error
+	namespaceListErr     error
 	httpLogOriginal      *config.HTTPLogSpec
 	resourceValue        string
 	originalID           string
@@ -137,6 +138,7 @@ type AddWizardState struct {
 	confirmationFocus    ConfirmationFocus
 	portAvailable        bool
 	isEditing            bool
+	namespaceManual      bool
 	loading              bool
 	httpLog              bool
 }
@@ -223,6 +225,13 @@ func (w *AddWizardState) handleTextInput(char rune) {
 	}
 }
 
+// isTypingText reports whether printable keys must go into a text field,
+// including keys that otherwise navigate (j, k).
+func (w *AddWizardState) isTypingText() bool {
+	return w.inputMode == InputModeText ||
+		(w.step == StepConfirmation && w.confirmationFocus == FocusAlias)
+}
+
 // clearTextInput clears the text input field
 func (w *AddWizardState) clearTextInput() {
 	w.textInput = ""