fix(primitives): eslint/tsconfig migration, asChild refactor, type fixes

- Migrate to eslint flat config + composite tsconfig.
- Complete the asChild→as="template" refactor (remove asChild prop + :as-child
  bindings across components, matching Primitive's slot model).
- Fix test type errors and source type-safety (useGraceArea hull/point math,
  FocusScope/util ref typing).

Note: ~53 vue-tsc errors remain (HTML attr/event passthrough typing on
transparent wrapper components + a couple of duplicate-export naming
collisions) — not gated by CI (build/lint/test green); pending a
component-attribute-typing design decision.

vue/primitives/src/menu/MenuGroup.vue

@@ -9,13 +9,13 @@ import { useId } from '../config-provider';
 import { Primitive } from '../primitive';
 import { provideMenuGroupContext } from './context';
 
-const { as = 'div', asChild } = defineProps<MenuGroupProps>();
+const { as = 'div' } = defineProps<MenuGroupProps>();
 const id = useId(undefined, 'menu-group');
 provideMenuGroupContext({ id: id.value });
 </script>
 
 <template>
-  <Primitive :as="as" :as-child="asChild" role="group" :id="id">
+  <Primitive :as="as" role="group" :id="id">
     <slot />
   </Primitive>
 </template>

vue/primitives/src/menu/MenuItemImpl.vue

@@ -21,7 +21,6 @@ const {
   disabled = false,
   textValue: textValueProp,
   as = 'div',
-  asChild,
 } = defineProps<MenuItemImplProps>();
 
 const emit = defineEmits<MenuItemImplEmits>();
@@ -71,11 +70,10 @@ function handleKeyDown(event: KeyboardEvent) {
 </script>
 
 <template>
-  <RovingFocusItem as-child :focusable="!disabled" :active="isHighlighted">
+  <RovingFocusItem :focusable="!disabled" :active="isHighlighted">
     <Primitive
       :ref="(el: unknown) => { itemRef = el as HTMLElement | null }"
       :as="as"
-      :as-child="asChild"
       role="menuitem"
       data-primitives-menu-item=""
       :data-primitive-menu-item-text-value="textValue"

vue/primitives/src/menu/MenuItemIndicator.vue

@@ -14,7 +14,7 @@ import { Primitive } from '../primitive';
 import { useMenuItemIndicatorContext } from './context';
 import { getCheckedState, isIndeterminate } from './utils';
 
-const { as = 'span', asChild, forceMount = false } = defineProps<MenuItemIndicatorProps>();
+const { as = 'span', forceMount = false } = defineProps<MenuItemIndicatorProps>();
 const ctx = useMenuItemIndicatorContext();
 const isPresent = computed(() => ctx.checkedState.value === true || isIndeterminate(ctx.checkedState.value));
 </script>
@@ -23,7 +23,6 @@ const isPresent = computed(() => ctx.checkedState.value === true || isIndetermin
   <Presence :present="forceMount || isPresent">
     <Primitive
       :as="as"
-      :as-child="asChild"
       :data-state="getCheckedState(ctx.checkedState.value)"
     >
       <slot />

vue/primitives/src/menu/MenuLabel.vue

@@ -7,11 +7,11 @@ export interface MenuLabelProps extends PrimitiveProps {}
 <script setup lang="ts">
 import { Primitive } from '../primitive';
 
-const { as = 'div', asChild } = defineProps<MenuLabelProps>();
+const { as = 'div' } = defineProps<MenuLabelProps>();
 </script>
 
 <template>
-  <Primitive :as="as" :as-child="asChild">
+  <Primitive :as="as">
     <slot />
   </Primitive>
 </template>

vue/primitives/src/menu/MenuRadioGroup.vue

@@ -16,7 +16,7 @@ import { computed, ref } from 'vue';
 import { Primitive } from '../primitive';
 import { provideMenuRadioGroupContext } from './context';
 
-const { modelValue, defaultValue, as = 'div', asChild } = defineProps<MenuRadioGroupProps>();
+const { modelValue, defaultValue, as = 'div' } = defineProps<MenuRadioGroupProps>();
 const emit = defineEmits<MenuRadioGroupEmits>();
 
 const local = ref(defaultValue);
@@ -32,7 +32,7 @@ provideMenuRadioGroupContext({
 </script>
 
 <template>
-  <Primitive :as="as" :as-child="asChild" role="group">
+  <Primitive :as="as" role="group">
     <slot />
   </Primitive>
 </template>

vue/primitives/src/menu/MenuSeparator.vue

@@ -7,11 +7,11 @@ export interface MenuSeparatorProps extends PrimitiveProps {}
 <script setup lang="ts">
 import { Primitive } from '../primitive';
 
-const { as = 'div', asChild } = defineProps<MenuSeparatorProps>();
+const { as = 'div' } = defineProps<MenuSeparatorProps>();
 </script>
 
 <template>
-  <Primitive :as="as" :as-child="asChild" role="separator" aria-orientation="horizontal">
+  <Primitive :as="as" role="separator" aria-orientation="horizontal">
     <slot />
   </Primitive>
 </template>

vue/primitives/src/menu/MenuSub.vue

@@ -26,7 +26,7 @@ const triggerId = useId(undefined, 'menu-sub-trigger');
 provideMenuContext({
   open: openRef,
   onOpenChange: v => emit('update:open', v),
-  content: shallowRef(null),
+  content: shallowRef<HTMLElement | null>(null),
   onContentChange: () => {},
 });
 

vue/primitives/src/menu/MenuSubTrigger.vue

@@ -8,7 +8,7 @@ export interface MenuSubTriggerProps extends MenuItemImplProps {}
 import { PopperAnchor } from '../popper';
 import { useMenuContentContext, useMenuContext, useMenuRootContext, useMenuSubContext } from './context';
 import MenuItemImpl from './MenuItemImpl.vue';
-import { SUB_CLOSE_KEYS, SUB_OPEN_KEYS, getOpenState, isPointerInGraceArea } from './utils';
+import { SUB_CLOSE_KEYS, SUB_OPEN_KEYS, getOpenState } from './utils';
 
 const props = defineProps<MenuSubTriggerProps>();
 
@@ -62,7 +62,7 @@ function handleKeyDown(event: KeyboardEvent) {
 </script>
 
 <template>
-  <PopperAnchor as-child>
+  <PopperAnchor>
     <MenuItemImpl
       v-bind="props"
       :id="subCtx.triggerId.value"