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/DropdownMenuSubContent.vue

@@ -0,0 +1,44 @@
+<script lang="ts">
+import type { MenuSubContentEmits, MenuSubContentProps } from '../menu';
+
+/**
+ * The floating surface for a submenu's items, positioned alongside its
+ * DropdownMenuSubTrigger. Place it inside a DropdownMenuSub.
+ */
+export interface DropdownMenuSubContentProps extends MenuSubContentProps {}
+export type DropdownMenuSubContentEmits = MenuSubContentEmits;
+</script>
+
+<script setup lang="ts">
+import type { CSSProperties } from 'vue';
+
+import { useForwardExpose } from '@robonen/vue';
+import { MenuSubContent } from '../menu';
+
+const props = defineProps<DropdownMenuSubContentProps>();
+const emit = defineEmits<DropdownMenuSubContentEmits>();
+useForwardExpose();
+
+const contentStyle: CSSProperties = {
+  '--primitives-dropdown-menu-content-transform-origin': 'var(--popper-transform-origin)',
+  '--primitives-dropdown-menu-content-available-width': 'var(--popper-available-width)',
+  '--primitives-dropdown-menu-content-available-height': 'var(--popper-available-height)',
+  '--primitives-dropdown-menu-trigger-width': 'var(--popper-anchor-width)',
+  '--primitives-dropdown-menu-trigger-height': 'var(--popper-anchor-height)',
+} as CSSProperties;
+</script>
+
+<template>
+  <MenuSubContent
+    v-bind="props"
+    :style="contentStyle"
+    @close-auto-focus="emit('closeAutoFocus', $event)"
+    @escape-key-down="emit('escapeKeyDown', $event)"
+    @pointer-down-outside="emit('pointerDownOutside', $event)"
+    @focus-outside="emit('focusOutside', $event)"
+    @interact-outside="emit('interactOutside', $event)"
+    @dismiss="emit('dismiss')"
+    @entry-focus="emit('entryFocus', $event)"
+    @open-auto-focus="emit('openAutoFocus', $event)"
+  ><slot /></MenuSubContent>
+</template>