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/dropdown-menu/DropdownMenuSubTrigger.vue

@@ -0,0 +1,22 @@
+<script lang="ts">
+import type { MenuSubTriggerProps } from '../menu';
+
+/**
+ * The item that opens its submenu on hover or ArrowRight and closes it on
+ * ArrowLeft. Renders like a regular item but opens DropdownMenuSubContent
+ * instead of emitting `select`.
+ */
+export interface DropdownMenuSubTriggerProps extends MenuSubTriggerProps {}
+</script>
+
+<script setup lang="ts">
+import { useForwardExpose } from '@robonen/vue';
+import { MenuSubTrigger } from '../menu';
+
+const props = defineProps<DropdownMenuSubTriggerProps>();
+useForwardExpose();
+</script>
+
+<template>
+  <MenuSubTrigger v-bind="props"><slot /></MenuSubTrigger>
+</template>