feat(primitives): media-editor components, category reorg, perf + type cleanup

Reorganize components into category folders (forms/canvas/overlays/etc.); add the
media-editor headless family (timeline, curve-editor, waveform, crop, color
picker, etc.); apply perf fixes (O(1) collection lookups, plain-object drag
state, gesture-leak teardown, shallowRef color state, rect caching) and replace
source `any` with proper types.

vue/primitives/src/menus/menubar/MenubarSub.vue

@@ -0,0 +1,44 @@
+<script lang="ts">
+import type { MenuSubEmits, MenuSubProps } from '../menu';
+
+/**
+ * Wraps a nested submenu, pairing a MenubarSubTrigger with its
+ * MenubarSubContent. Owns the submenu's open state: bind `v-model:open` to
+ * control it, set `defaultOpen` to start open in uncontrolled mode, or leave
+ * both unset to let it manage its own open state. The default slot exposes the
+ * current `open` value.
+ */
+export interface MenubarSubProps extends MenuSubProps {
+  /** Open state when initially rendered. Use when you do not control `open`. */
+  defaultOpen?: boolean;
+}
+export type MenubarSubEmits = MenuSubEmits;
+</script>
+
+<script setup lang="ts">
+import { ref } from 'vue';
+
+import { MenuSub } from '../menu';
+
+const { defaultOpen = false } = defineProps<MenubarSubProps>();
+defineSlots<{ default?: (props: { open: boolean }) => unknown }>();
+
+const localOpen = ref<boolean>(defaultOpen);
+
+const open = defineModel<boolean>('open', {
+  default: undefined,
+  // Controlled when `v-model:open` is bound; otherwise the local ref (seeded
+  // from `defaultOpen`) drives it — uncontrolled mode with an initial state.
+  get: external => external ?? localOpen.value,
+  set: (value) => {
+    localOpen.value = value;
+    return value;
+  },
+});
+</script>
+
+<template>
+  <MenuSub :open="open" @update:open="open = $event">
+    <slot :open="open" />
+  </MenuSub>
+</template>