🎯 Changes

Fix props passed to withForm and withFieldGroup components not being reactive. (closes #2054)

withForm and withFieldGroup used object spread ({ ...props, ...innerProps })
to pass props to the render function.

In SolidJS, JSX props are passed as getter functions internally.
Object spread eagerly evaluates those getters and copies only the resulting values,
which breaks signal tracking.

// Parent component
<InstituteForm status={status()} />

// SolidJS compiles this to
createComponent(InstituteForm, {
  get status() { return status() }  // reactive getter
})

// But spread evaluates the getter immediately, producing a static value
{ ...innerProps }  →  { status: 'idle' }  // reactivity lost

As a result, even when the parent updates a signal, createEffect inside render
never re-runs and the JSX never updates.

Replace object spread with mergeProps() to preserve the reactive getters,
and call render via createComponent() to maintain the correct SolidJS
reactive context.

  // Before
  return (innerProps) => render({ ...props, ...innerProps })

  // After
  return (innerProps) => createComponent(
    render as Component<any>,
    mergeProps(props ?? {}, innerProps)
  )

The same fix is applied to withFieldGroup.

Add regression tests to verify JSX reactivity and createEffect re-runs
when signal props change in withForm and withFieldGroup.

✅ Checklist

• I have followed the steps in the Contributing guide.
• I have tested this code locally with pnpm test:pr.

🚀 Release Impact

• This change affects published code, and I have generated a changeset.
• This change is docs/CI/dev-only (no release).