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/composables/useInteractionState.ts

@@ -0,0 +1,40 @@
+import type { Ref, WatchSource } from 'vue';
+import { onScopeDispose, shallowRef, watch } from 'vue';
+import type { Viewport } from '../types';
+
+/**
+ * True while the viewport is actively panning/zooming, flipped back to `false`
+ * `idleDelay` ms after the last change. Driven purely by viewport mutations, so
+ * it covers every path — wheel, pinch, drag-pan, double-click and the imperative
+ * `zoomIn`/`zoomTo`/`fitView` API — without each call site having to opt in.
+ *
+ * Used to gate `will-change: transform` on `FlowViewport`. Keeping that hint on
+ * permanently pins the compositor's raster scale: the layer is rasterised once
+ * and the `scale(zoom)` is applied by GPU-upscaling that cached texture, so at
+ * high zoom every node and edge stays blurry even after the gesture ends.
+ * Toggling the hint on only while interacting lets the browser re-rasterise the
+ * layer crisply once motion settles — the same pattern `FlowNode` already uses
+ * for its drag transform.
+ */
+export function useInteractionState(
+  source: WatchSource<Viewport>,
+  idleDelay = 200,
+): Readonly<Ref<boolean>> {
+  const interacting = shallowRef(false);
+  let timer: ReturnType<typeof setTimeout> | undefined;
+
+  watch(source, () => {
+    interacting.value = true;
+    if (timer !== undefined) clearTimeout(timer);
+    timer = setTimeout(() => {
+      interacting.value = false;
+      timer = undefined;
+    }, idleDelay);
+  });
+
+  onScopeDispose(() => {
+    if (timer !== undefined) clearTimeout(timer);
+  });
+
+  return interacting;
+}