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/utilities/dismissable-layer/index.ts

@@ -0,0 +1,12 @@
+export { default as DismissableLayer } from './DismissableLayer.vue';
+export { default as DismissableLayerBranch } from './DismissableLayerBranch.vue';
+export { dismissableLayerStack } from './stack';
+
+export type {
+  DismissableLayerEmits,
+  DismissableLayerProps,
+} from './DismissableLayer.vue';
+
+export type {
+  DismissableLayerBranchProps,
+} from './DismissableLayerBranch.vue';