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/playground/src/demos/Checkbox.vue

@@ -1,7 +1,7 @@
 <script setup lang="ts">
 import { ref } from 'vue';
-import type { CheckedState } from '@primitives/checkbox';
-import { CheckboxIndicator, CheckboxRoot } from '@primitives/checkbox';
+import type { CheckedState } from '@primitives/forms/checkbox';
+import { CheckboxIndicator, CheckboxRoot } from '@primitives/forms/checkbox';
 
 const checked = ref<CheckedState>(false);
 const disabled = ref(false);