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/selection/select/SelectLabel.vue

@@ -0,0 +1,31 @@
+<script lang="ts">
+import type { PrimitiveProps } from '../../internal/primitive';
+
+/**
+ * A non-selectable heading for a `SelectGroup`. Renders the text that labels the
+ * group and wires its id to the group's `aria-labelledby`; must be used inside a
+ * `SelectGroup`.
+ */
+export interface SelectLabelProps extends PrimitiveProps {}
+</script>
+
+<script setup lang="ts">
+import { useForwardExpose } from '@robonen/vue';
+
+import { Primitive } from '../../internal/primitive';
+import { useSelectGroupContext } from './context';
+
+const { as = 'div' } = defineProps<SelectLabelProps>();
+const { forwardRef } = useForwardExpose();
+const groupCtx = useSelectGroupContext();
+</script>
+
+<template>
+  <Primitive
+    :ref="forwardRef"
+    :as="as"
+    :id="groupCtx.id.value"
+  >
+    <slot />
+  </Primitive>
+</template>