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/SelectValue.vue

@@ -0,0 +1,63 @@
+<script lang="ts">
+import type { PrimitiveProps } from '../../internal/primitive';
+
+/**
+ * Displays the label(s) of the currently selected option(s) inside the trigger,
+ * or the `placeholder` when nothing is selected. Renders into a non-interactive
+ * span so pointer events fall through to the trigger. Exposes the resolved
+ * `selectedLabel` array and raw `modelValue` to its default slot for custom
+ * rendering (e.g. multi-value chips), and reflects a `data-placeholder`
+ * attribute while empty.
+ */
+export interface SelectValueProps extends PrimitiveProps {
+  /** Text shown when no option is selected. */
+  placeholder?: string;
+}
+</script>
+
+<script setup lang="ts">
+import { computed, watchPostEffect } from 'vue';
+
+import { useForwardExpose } from '@robonen/vue';
+import { Primitive } from '../../internal/primitive';
+import { useSelectRootContext } from './context';
+import { valueComparator } from './utils';
+
+const { as = 'span', placeholder = '' } = defineProps<SelectValueProps>();
+
+const { forwardRef, currentElement } = useForwardExpose();
+const rootCtx = useSelectRootContext();
+
+watchPostEffect(() => rootCtx.onValueElementChange(currentElement.value));
+
+const selectedLabel = computed<string[]>(() => {
+  const options = Array.from(rootCtx.optionsSet.value);
+  const labelFor = (v: unknown) =>
+    options.find(option => valueComparator(v as never, option.value as never, rootCtx.by as never))?.textContent ?? '';
+
+  const current = rootCtx.value.value;
+  if (Array.isArray(current)) {
+    return current.map(labelFor).filter(Boolean);
+  }
+  // Fall back to the persisted single-value label so a freshly-selected value
+  // keeps showing after the listbox (and its items) unmount.
+  const fromOptions = current === undefined ? '' : labelFor(current);
+  const resolved = fromOptions || (rootCtx.displayValue.value ?? '');
+  return resolved ? [resolved] : [];
+});
+
+const slotText = computed(() => (selectedLabel.value.length ? selectedLabel.value.join(', ') : placeholder));
+</script>
+
+<template>
+  <Primitive
+    :ref="forwardRef"
+    :as="as"
+    style="pointer-events: none"
+    :data-placeholder="selectedLabel.length ? undefined : placeholder"
+  >
+    <slot :selected-label="selectedLabel" :model-value="rootCtx.value.value">
+      {{ slotText }}
+    </slot>
+  </Primitive>
+</template>