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/canvas/flow/FlowPanel.vue

@@ -0,0 +1,60 @@
+<script lang="ts">
+import type { CSSProperties } from 'vue';
+import type { PrimitiveProps } from '../../internal/primitive';
+
+export type FlowPanelPosition
+  = | 'top-left' | 'top-center' | 'top-right'
+    | 'bottom-left' | 'bottom-center' | 'bottom-right';
+
+/**
+ * An absolutely-positioned overlay anchored to a corner/edge of the pane, for
+ * chrome like controls, legends, or toolbars. Stops pointer/wheel events from
+ * reaching the pane, so interacting with the panel never pans or zooms. Place
+ * inside `FlowRoot`'s default slot.
+ */
+export interface FlowPanelProps extends PrimitiveProps {
+  /** Anchor position within the pane. @default 'top-left' */
+  position?: FlowPanelPosition;
+}
+</script>
+
+<script setup lang="ts">
+import { computed } from 'vue';
+import { useForwardExpose } from '@robonen/vue';
+import { Primitive } from '../../internal/primitive';
+
+const { position = 'top-left', as = 'div' } = defineProps<FlowPanelProps>();
+const { forwardRef } = useForwardExpose();
+
+const style = computed<CSSProperties>(() => {
+  const [v, h] = position.split('-') as ['top' | 'bottom', 'left' | 'center' | 'right'];
+  const s: CSSProperties = { position: 'absolute', pointerEvents: 'all' };
+  s[v] = '0';
+  if (h === 'center') {
+    s.left = '50%';
+    s.transform = 'translateX(-50%)';
+  }
+  else {
+    s[h] = '0';
+  }
+  return s;
+});
+
+function stop(event: Event): void {
+  event.stopPropagation();
+}
+</script>
+
+<template>
+  <Primitive
+    :ref="forwardRef"
+    :as="as"
+    data-flow-panel=""
+    :data-position="position"
+    :style="style"
+    @pointerdown="stop"
+    @wheel="stop"
+  >
+    <slot />
+  </Primitive>
+</template>