chore: add create-crud-page and form-patterns skills, refresh CLAUDE.md

.claude/skills/form-patterns/SKILL.md

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+---
+name: form-patterns
+description: Patterns for forms with cascading/dependent selections in the gpustack-ui monorepo. Use when building a form where picking one field derives another (pick A → auto-pick B → write form), handling async option loading on modal open, or protecting against stale async results.
+---
+
+# Form Patterns
+
+Theme: keep cascading selections (pick A → derive B → write form) on a single, predictable path.
+
+## Accessing the form: `form` vs `form.current`
+
+This is **not** absolute — it depends on the call site:
+
+- **Inside the form component** (`forms/index.tsx`), or anywhere holding a `Form.useForm()` instance → call it directly: `form.setFieldsValue(...)`.
+- **In the outer Drawer/Modal wrapper** that opens the form and holds it via `ref={form}` (`const form = useRef(null)`), driven by an `open` prop → go through the ref: `form.current?.setFieldsValue(...)`.
+
+The reference template below is written for the **Drawer-wrapper scenario** (it reacts to `open` and owns the shared `selection` state), so it uses `form.current?` throughout. If you lift this logic into the form body with a `useForm()` instance, drop the `.current`.
+
+## 1. No fallback for derived selection
+
+When "pick A then auto-pick B", match by rule and return `undefined` if no match — let the form field stay empty. Do **not** silently fall back to `list[0]`; a fallback hides data issues and fakes a valid selection.
+
+```ts
+const findB = (key, list) =>
+  key ? list.find((x) => x.key === key) : undefined;
+```
+
+For form fields, clear with `undefined`, not `''`. In Ant Design `undefined` restores the placeholder; `''` is treated as a real value.
+
+## 2. Async race protection
+
+For fetches triggered by a lifecycle entry (e.g. modal open), tag each invocation with a session ref. Discard stale results if the session rotated (modal closed and re-opened) before the response arrives.
+
+```ts
+const sessionRef = useRef(0);
+
+useEffect(() => {
+  if (!open) {
+    sessionRef.current += 1;
+    return;
+  }
+  const session = ++sessionRef.current;
+  Promise.all([fetchA(), fetchB()]).then(([as, bs]) => {
+    if (sessionRef.current !== session) return;
+    applySelection(as.items[0], findB(as.items[0].key, bs.items));
+  });
+}, [open]);
+```
+
+## 3. Reference template
+
+Two cascading selectors backed by a single shared state, with a single atomic write (state + form together):
+
+```ts
+type Selection = { a?: string; b?: number };
+
+const [selection, setSelection] = useState<Selection>({});
+const sessionRef = useRef(0);
+const form = useRef<any>(null); // wrapper holds the form via <Form ref={form} /> — see "Accessing the form" above
+
+const findB = (key, list) =>
+  key ? list.find((x) => x.key === key) : undefined;
+
+// Single atomic write: state + form together.
+const applySelection = (a, b) => {
+  setSelection({ a: a.name, b: b?.id });
+  form.current?.setFieldsValue({
+    field: b?.field,
+    spec: { ...currentSpec, ...b?.spec }
+  });
+};
+
+// Trigger 1: modal opened
+useEffect(() => {
+  if (!open) {
+    sessionRef.current++;
+    setSelection({});
+    return;
+  }
+  const session = ++sessionRef.current;
+  Promise.all([fetchA(), fetchB()]).then(([as, bs]) => {
+    if (sessionRef.current !== session) return;
+    const first = as.items[0];
+    applySelection(first, findB(first.key, bs.items));
+  });
+}, [open]);
+
+// Trigger 2: user picks A
+const handleAChange = (a) => {
+  applySelection(a, findB(a.key, listB));
+};
+
+// Trigger 3: user picks B
+const handleBChange = (b) => {
+  setSelection((prev) => ({ ...prev, b: b.id }));
+  form.current?.setFieldsValue({ ...b.fields });
+};
+```
+
+## Related
+
+- Module/file structure for forms lives in the **create-crud-page** skill (section 3).
+- Required-field validation: use `getRuleMessage`.