fix(studio,core): audio has timing, not motion — and a bus has neither

Selecting an audio bus showed a Motion section offering tween editors. A
bus has no transform, opacity or box, so every effect on that list moves
nothing; the same is true of an `<audio>` clip.

The panel's gate was "are the GSAP handlers wired", and `App.tsx` always
wires them, so it was true for every selection. It now also asks what was
selected.

Audio keeps its timing — an `<audio>` clip is placed on the timeline like
anything else — but the section is called Timing there and summarises its
span instead of an effect count, because "Motion: 0 effects" on a sound
is a category error. A bus loses timing too: it has no `data-start` and
no duration, and its automation clock is composition time, so Start /
Duration / End would be editing nothing.

Gated on the TAG, not on `sections.animation`: a `div` with no tweens yet
must still offer "+ Add", and keying the rename on `animationCount > 0`
renamed the section for exactly that div — which the existing panel test
caught. Keying it on `showMotionEffects` renamed it for an `img`, which
wires no GSAP handlers. Both halves belong to the tag.

`affordances.ts` carries the same two rules for anything reading the
section list rather than the flat panel. The label pair is
`motionSectionLabel`, in the module that owns the section it names, which
is also what keeps `PropertyPanelFlat.tsx` under the 600-line ceiling.

packages/studio/src/components/editor/PropertyPanel.test.tsx

@@ -177,6 +177,39 @@ function sixGroupElement() {
   };
 }
 
+/** An `<audio>` clip: placed on the timeline, but nothing a tween could move. */
+function audioClipElement() {
+  return {
+    ...baseElement(),
+    id: "vo-1",
+    selector: "#vo-1",
+    label: "Vo 1",
+    tagName: "audio",
+    textFields: [],
+    dataAttributes: { start: "1", duration: "3" },
+  };
+}
+
+/**
+ * A mixer bus: no clip range at all, and no box either.
+ *
+ * Carries a `data-start` on purpose. A real bus has none — its automation clock
+ * is composition time — but the timing gate has to refuse the TAG rather than
+ * merely fall out of a missing attribute, or something writing one would put
+ * Start/Duration back on a thing that has no range.
+ */
+function audioBusElement() {
+  return {
+    ...baseElement(),
+    id: "voiceover",
+    selector: "#voiceover",
+    label: "Voiceover",
+    tagName: "hf-audio-group",
+    textFields: [],
+    dataAttributes: { start: "0", duration: "8" },
+  };
+}
+
 const INFERRED_TIMING_ANIMATION = {
   id: "a1",
   targetSelector: "#inferred-anim",
@@ -951,3 +984,39 @@ describe("PropertyPanel — flat group entrance animation scoping (fix round)",
     RENDER_TIMEOUT_MS,
   );
 });
+
+describe("PropertyPanel — Motion is for things that move", () => {
+  it(
+    "calls the section Timing on an audio clip, and offers no tween editor",
+    async () => {
+      const { host, root } = await renderPanel(true, audioClipElement());
+      const titles = Array.from(
+        host.querySelectorAll<HTMLElement>("[data-flat-group-collapsed], [data-flat-group-open]"),
+      ).map((el) => el.textContent ?? "");
+      // The clip's placement survives — it is still a clip on a track.
+      expect(titles.some((t) => t.includes("Timing"))).toBe(true);
+      // "Motion" named the tween editor, which an <audio> element has no
+      // transform, opacity or box for. Showing it was the panel gating on
+      // handler presence rather than on the element.
+      expect(titles.some((t) => t.includes("Motion"))).toBe(false);
+      act(() => root.unmount());
+    },
+    RENDER_TIMEOUT_MS,
+  );
+
+  it(
+    "offers a bus neither — it has no clip range to edit",
+    async () => {
+      const { host, root } = await renderPanel(true, audioBusElement());
+      const titles = Array.from(
+        host.querySelectorAll<HTMLElement>("[data-flat-group-collapsed], [data-flat-group-open]"),
+      ).map((el) => el.textContent ?? "");
+      expect(titles.some((t) => t.includes("Motion"))).toBe(false);
+      expect(titles.some((t) => t.includes("Timing"))).toBe(false);
+      // It is still a mixer bus: the reason to select one at all.
+      expect(titles.some((t) => t.includes("Audio FX"))).toBe(true);
+      act(() => root.unmount());
+    },
+    RENDER_TIMEOUT_MS,
+  );
+});

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

@@ -15,7 +15,7 @@ import { FlatGroupHeader } from "./propertyPanelFlatPrimitives";
 import { FlatTextSection } from "./propertyPanelFlatTextSection";
 import { FlatStyleSection } from "./propertyPanelFlatStyleSections";
 import { FlatLayoutSection } from "./propertyPanelFlatLayoutSection";
-import { FlatMotionSection } from "./propertyPanelFlatMotionSection";
+import { FlatMotionSection, motionSectionLabel } from "./propertyPanelFlatMotionSection";
 import { AudioFxGroup } from "./propertyPanelAudioFxGroup.js";
 import { useVolumeAutomation } from "./useVolumeAutomation";
 import { useAudioFxRevealSection } from "./useAudioFxRevealSection";
@@ -282,7 +282,16 @@ export function PropertyPanelFlat({
           onSetAllKeyframeEases,
         }
       : null;
-  const showMotionEffects = gsapEffectHandlers !== null;
+  const selectedTag = element.tagName?.toLowerCase();
+  const audioSelection = selectedTag === "audio" || selectedTag === HF_AUDIO_GROUP_TAG;
+  // Handlers being wired is necessary but not sufficient: App.tsx always passes
+  // them, so this alone showed the tween editor for every selection — including
+  // an `<audio>` clip and an `<hf-audio-group>` bus, neither of which has a
+  // transform, an opacity or a box for a tween to move. Gated on the TAG, not on
+  // `sections.animation` (`animationCount > 0`): a div with no tweens yet must
+  // still offer "+ Add", so "has none" and "can have none" are different
+  // questions and only the second one belongs here.
+  const showMotionEffects = gsapEffectHandlers !== null && !audioSelection;
   const showMotionGroup = showMotionTiming || showMotionEffects;
 
   const volumeAutomation = useVolumeAutomation(element, onSetAttributeQuiet ?? onSetAttributeLive);
@@ -298,9 +307,6 @@ export function PropertyPanelFlat({
     return resolveAudioGroups(doc).find((g) => g.memberIds.includes(id))?.label;
   })();
 
-  const selectedTag = element.tagName?.toLowerCase();
-  const audioSelection = selectedTag === "audio" || selectedTag === HF_AUDIO_GROUP_TAG;
-
   const groups: FlatGroupDescriptor[] = [];
   if (isTextEditable) {
     groups.push({
@@ -388,8 +394,12 @@ export function PropertyPanelFlat({
   if (showMotionGroup) {
     groups.push({
       id: "motion",
-      title: "Motion",
-      summary: `${gsapAnimations.length} effect${gsapAnimations.length === 1 ? "" : "s"}`,
+      ...motionSectionLabel({
+        timingOnly: audioSelection,
+        start: elStart,
+        duration: elDuration,
+        effectCount: gsapAnimations.length,
+      }),
       content: (
         <FlatMotionSection
           element={element}

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

@@ -172,3 +172,34 @@ export function FlatMotionSection({
     </div>
   );
 }
+
+/**
+ * What the Motion section is called, and what its collapsed line says.
+ *
+ * "Motion" names the tween editor. On audio the section is Start/Duration/End
+ * and nothing else, so the label would promise what it no longer offers — and
+ * "Motion: 0 effects" on a sound is a category error, hence the span instead of
+ * a count.
+ *
+ * Keyed on the TAG by its caller, not on whether the effects half is showing:
+ * that half also disappears when a host simply has not wired the GSAP handlers,
+ * and a div in that state is still a thing that moves — renaming its section
+ * would be describing the host's wiring rather than the element.
+ */
+export function motionSectionLabel(args: {
+  timingOnly: boolean;
+  start: number;
+  duration: number;
+  effectCount: number;
+}): { title: string; summary: string } {
+  if (args.timingOnly) {
+    return {
+      title: "Timing",
+      summary: `${formatTimingValue(args.start)} – ${formatTimingValue(args.start + args.duration)}`,
+    };
+  }
+  return {
+    title: "Motion",
+    summary: `${args.effectCount} effect${args.effectCount === 1 ? "" : "s"}`,
+  };
+}