Added AI skills

.agents/skills/react-hook-form/references/array-use-field-id-as-key.md

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+---
+title: Use field.id as Key in useFieldArray Maps
+impact: MEDIUM-HIGH
+impactDescription: prevents state corruption and unnecessary re-renders
+tags: array, useFieldArray, key, react-key
+---
+
+## Use field.id as Key in useFieldArray Maps
+
+useFieldArray generates a unique `id` for each field. Using array index as key causes React to lose track of component identity when items are reordered, removed, or inserted.
+
+**Incorrect (index as key causes state corruption):**
+
+```typescript
+function IngredientsForm() {
+  const { control, register } = useForm()
+  const { fields, append, remove } = useFieldArray({ control, name: 'ingredients' })
+
+  return (
+    <div>
+      {fields.map((field, index) => (
+        <div key={index}>  {/* Index key causes re-render issues */}
+          <input {...register(`ingredients.${index}.name`)} />
+          <button type="button" onClick={() => remove(index)}>Remove</button>
+        </div>
+      ))}
+      <button type="button" onClick={() => append({ name: '' })}>Add</button>
+    </div>
+  )
+}
+```
+
+**Correct (field.id ensures stable identity):**
+
+```typescript
+function IngredientsForm() {
+  const { control, register } = useForm()
+  const { fields, append, remove } = useFieldArray({ control, name: 'ingredients' })
+
+  return (
+    <div>
+      {fields.map((field, index) => (
+        <div key={field.id}>  {/* Stable identity across operations */}
+          <input {...register(`ingredients.${index}.name`)} />
+          <button type="button" onClick={() => remove(index)}>Remove</button>
+        </div>
+      ))}
+      <button type="button" onClick={() => append({ name: '' })}>Add</button>
+    </div>
+  )
+}
+```
+
+**Forward compatibility:** `field.id` is correct for all of v7. The v8 beta line renames the generated render key to `field.key` and drops the `keyName` option, so `id` becomes an ordinary data property that no longer guarantees uniqueness. Do not pre-emptively switch on v7 — but if you set `keyName` to something custom today, that is the piece with no v8 equivalent.
+
+Reference: [useFieldArray](https://react-hook-form.com/docs/usefieldarray)