[dashboard] Kubernetes app: clearing instanceType to size a node group by explicit resources silently fails to save #3135

Summary

In the dashboard (console) Kubernetes app form, a user who wants to size a worker node group by explicit resources (cpu/memory) instead of an instanceType cannot do it: clearing the instanceType field and entering cpu/memory makes the Save button silently do nothing — no toast, no navigation, no validation error.

This is the apps/kubernetes analog of #2909 (same class of problem reported for vm-instance).

Steps to reproduce

1. Open the Kubernetes app create/edit form in the console.
2. On a worker node group, clear the instanceType field and set resources.cpu / resources.memory.
3. Click Save → nothing happens (no error surfaced, form not submitted).

Mechanism (console)

The app form is schema-driven (RJSF) over the app's values.schema.json:

• nodeGroups[].instanceType is required in the schema (and defaulted to u1.medium).
• packages/system/dashboard/images/console/apps/console/src/components/SchemaForm.tsx sets liveValidate={false}, so validation runs on submit. An empty value for a required field fails validation and onSubmit never fires — the click is a silent no-op with no visible error.
• …/components/DynamicOptionsWidget.tsx renders the empty choice as <option value="" disabled={required}>, so for the required instanceType field the "-- None --" option is disabled — the field cannot even be emptied through the dropdown.

Net effect: the dashboard offers no way to size a node group purely by resources, and the blocked submit is silent.

Relationship to #3121 and #2909

• fix(kubernetes): make node group resources optional when instanceType is set #3121 (chart, precedence) makes sizing by resources work when the default instanceType is kept: explicit resources take precedence and the instancetype is omitted at render, so the VM is valid. That resolves the practical workflow. It deliberately keeps instanceType required (no schema/UI change), so the dashboard still cannot represent "no instanceType, size by resources," and clearing the field still fails silently.
• vm-instance renders both instancetype matcher and explicit domain resources — KubeVirt rejects the VM with a conflict error #2909 is the same defect for vm-instance (area/dashboard, accepted).

Suggested fix (one or both)

1. Surface the failure. A schema-driven form should show validation errors (or focus the offending field) on a blocked submit instead of silently doing nothing. This applies to every app form, not just Kubernetes, and is the higher-value fix.
2. Allow sizing by resources from the UI. If clearing instanceType is meant to be supported, drop instanceType from the schema required list — DynamicOptionsWidget already enables a selectable "-- None --" when the field is not required — paired with a render-time "at least one sizing source" guard in the chart. With fix(kubernetes): make node group resources optional when instanceType is set #3121's precedence landing, this is optional polish.

Environment

Reproducible on current main console (packages/system/dashboard/images/console). Originally surfaced on the apps/kubernetes node-group form.