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/context-menu/ContextMenuCheckboxItem.vue

@@ -0,0 +1,26 @@
+<script lang="ts">
+import type { MenuCheckboxItemEmits, MenuCheckboxItemProps } from '../menu';
+
+/**
+ * An item that toggles an on/off (or indeterminate) state, exposing
+ * `aria-checked` for assistive tech. Bind `v-model:checked` and pair it with a
+ * `ContextMenuItemIndicator` to render the checkmark.
+ */
+export interface ContextMenuCheckboxItemProps extends MenuCheckboxItemProps {}
+export type ContextMenuCheckboxItemEmits = MenuCheckboxItemEmits;
+</script>
+
+<script setup lang="ts">
+import { MenuCheckboxItem } from '../menu';
+
+const props = defineProps<ContextMenuCheckboxItemProps>();
+const emit = defineEmits<ContextMenuCheckboxItemEmits>();
+</script>
+
+<template>
+  <MenuCheckboxItem
+    v-bind="props"
+    @select="emit('select', $event)"
+    @update:checked="emit('update:checked', $event)"
+  ><slot /></MenuCheckboxItem>
+</template>