Background

As part of #3017, the first sub-area to split out is the form infrastructure itself.

Current dependency points include:

• src/components/ui/form/UIForm.vue
• src/components/ui/form/UIFormItem.vue
• src/components/ui/form/UIFormItemInternal.vue

Problem

This part is more than a thin wrapper over naive-ui.

Current implementation details include:

• UIForm wraps NForm
• UIFormItem wraps NFormItem
• UIFormItemInternal imports formItemInjectionKey from naive-ui/es/_mixins/use-form-item
• we hijack the internal form-item injection to intercept blur/input behavior
• validation timing includes custom blur delay, debounced input validation, and IME composition handling

This means the form infrastructure depends not only on public naive-ui components, but also on internal APIs that are especially fragile.

Goal

Replace the naive-ui form container / form item infrastructure with an internal implementation that preserves the behavior expected by the rest of XBuilder.

Scope

• replace NForm usage in UIForm
• replace NFormItem usage in UIFormItem
• remove the dependency on formItemInjectionKey and other naive-ui internal plumbing
• preserve current validation behavior, including submit flow, validation state display, blur/input-triggered validation, and IME-safe handling

Notes

This issue is about form orchestration and validation plumbing. Specific input controls should be handled in separate child issues.