Added AI skills

.agents/skills/react-hook-form/references/formcfg-should-unregister.md

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+---
+title: Keep shouldUnregister Off Unless Hidden Fields Must Leave the Payload
+impact: HIGH
+impactDescription: prevents silently dropping values the user already entered
+tags: formcfg, should-unregister, dynamic-forms, conditional-fields
+---
+
+## Keep shouldUnregister Off Unless Hidden Fields Must Leave the Payload
+
+The default (`shouldUnregister: false`) keeps a field's value in form state after its input unmounts. That is the right default and it is not a memory problem — the retained data is a few strings per field. `shouldUnregister: true` is a **submission-shape** option: it removes unmounted fields from the values object entirely. Reaching for it to "clean up" a multi-step wizard silently deletes everything the user entered on step 1 the moment they advance to step 2.
+
+**Incorrect (wizard loses step 1 the moment step 2 renders):**
+
+```typescript
+function OnboardingWizard() {
+  const [step, setStep] = useState(1)
+  const { register, handleSubmit } = useForm<OnboardingData>({
+    shouldUnregister: true,  // personalName is dropped as soon as step 1 unmounts
+    defaultValues: { personalName: '', companyName: '' },
+  })
+
+  return (
+    <form onSubmit={handleSubmit(completeOnboarding)}>
+      {step === 1 && <input {...register('personalName')} />}
+      {step === 2 && <input {...register('companyName')} />}
+      <button type="button" onClick={() => setStep(2)}>Next</button>
+    </form>
+  )
+}
+```
+
+**Correct (default retention — every step survives to submit):**
+
+```typescript
+function OnboardingWizard() {
+  const [step, setStep] = useState(1)
+  const { register, handleSubmit } = useForm<OnboardingData>({
+    defaultValues: { personalName: '', companyName: '' },
+  })
+
+  return (
+    <form onSubmit={handleSubmit(completeOnboarding)}>
+      {step === 1 && <input {...register('personalName')} />}
+      {step === 2 && <input {...register('companyName')} />}
+      <button type="button" onClick={() => setStep(2)}>Next</button>
+    </form>
+  )
+}
+```
+
+**When `shouldUnregister: true` is the right call:**
+- A discriminated payload where the hidden branch's keys must be absent, not empty — e.g. a "Business" account sends `taxId` and a "Personal" one must not send the key at all
+- A backend that treats a present-but-empty key differently from an absent one
+- Set it per field via `register('taxId', { shouldUnregister: true })` rather than form-wide, so the rest of the form keeps the safe default
+
+Reference: [useForm - shouldUnregister](https://react-hook-form.com/docs/useform)