refactor(studio): lift audioFxSummary out of PropertyPanelFlat

`PropertyPanelFlat.tsx` is 612 lines here against the repo's 600-line cap,
so the required File size check is red — the sole reason this PR is
blocked. The review says as much: "mechanical fix (~5 min), not a design
problem. Code itself is LGTM."

Moves `audioFxSummary` to `audioFxSummary.ts`, the same file a later
branch creates for it. Deliberately the smallest cut that clears the cap
rather than the whole `AudioFxGroup` extraction: every later commit in the
stack edits AudioFxGroup, so moving it here would collide with each of
them, while almost nothing touches this function.

595 lines.

Author: vanceingalls

packages/studio/src/components/editor/PropertyPanelFlat.tsx

@@ -24,6 +24,7 @@ import {
   normalizeCarveSettings,
   type HfCarveSettings,
 } from "@hyperframes/core/audio-carve";
+import { audioFxSummary } from "./audioFxSummary";
 import { FlatMediaSection } from "./propertyPanelFlatMediaSection";
 import type { DomEditSelection } from "./domEditing";
 import { FxSection, type AudioTrackOption } from "./propertyPanelFxSection";
@@ -536,24 +537,6 @@ export function PropertyPanelFlat({
   );
 }
 
-/** Chain length at a glance, so the collapsed group says whether anything is on. */
-function audioFxSummary(element: DomEditSelection): string {
-  const raw = element.dataAttributes?.["fx-chain"];
-  const carve = element.dataAttributes?.["fx-carve"];
-  let count = 0;
-  if (raw) {
-    try {
-      count = parseAudioFxChain(raw).nodes.filter((n) => n.enabled !== false).length;
-    } catch {
-      return "unreadable";
-    }
-  }
-  const parts: string[] = [];
-  if (count > 0) parts.push(`${count} effect${count === 1 ? "" : "s"}`);
-  if (carve) parts.push("carve");
-  return parts.length > 0 ? parts.join(" + ") : "none";
-}
-
 /**
  * Bridges the FX panel to the element/attribute world. Chain and carve are
  * serialised onto the element the way colour grading carries its config, so

packages/studio/src/components/editor/audioFxSummary.ts

@@ -0,0 +1,27 @@
+/**
+ * What the collapsed Audio FX group says it holds.
+ *
+ * Its own module because `PropertyPanelFlat.tsx` is at the repo's 600-line
+ * budget, and this is the piece with no dependency on the panel around it.
+ */
+
+import { parseAudioFxChain } from "@hyperframes/core/audio-fx";
+import type { DomEditSelection } from "./domEditing";
+
+/** Chain length at a glance, so the collapsed group says whether anything is on. */
+export function audioFxSummary(element: DomEditSelection): string {
+  const raw = element.dataAttributes?.["fx-chain"];
+  const carve = element.dataAttributes?.["fx-carve"];
+  let count = 0;
+  if (raw) {
+    try {
+      count = parseAudioFxChain(raw).nodes.filter((n) => n.enabled !== false).length;
+    } catch {
+      return "unreadable";
+    }
+  }
+  const parts: string[] = [];
+  if (count > 0) parts.push(`${count} effect${count === 1 ? "" : "s"}`);
+  if (carve) parts.push("carve");
+  return parts.length > 0 ? parts.join(" + ") : "none";
+}