fix(studio): span the clip on the remaining duration-less tween paths

Two sibling call paths still answered from GSAP's 0.5s default while the
toggle path had moved to the clip-wide fallback.

isPlayheadWithinTween now takes the selection, so the toolbar stops
promising "extends animation" on a duration-less tween whose click actually
toggles an interior keyframe. The arc drag commit resolves its replacement
duration the same way its click-path sibling does, instead of authoring
duration 0.5 and collapsing the arc window.

The flat text section drops its two marker-clearing effects: the autofocus
marker is a ref now, read and cleared by the render that consumes it.

packages/studio/src/hooks/gsapDragPositionCommit.ts

@@ -4,6 +4,7 @@ import { usePlayerStore } from "../player/store/playerStore";
 import { resolveTweenStart, resolveTweenDuration } from "../utils/globalTimeCompiler";
 import { roundTo3 } from "../utils/rounding";
 import { computeDraggedGsapPosition } from "./draggedGsapPosition";
+import { resolveEditableTweenDuration } from "./gsapShared";
 import {
   type GsapDragCommitCallbacks,
   computeCurrentPercentage,
@@ -297,7 +298,9 @@ export async function commitGsapPositionFromDrag(
     }
 
     const tweenStart = resolveTweenStart(anim);
-    const tweenDuration = resolveTweenDuration(anim);
+    // Clip-wide, same as applyArcKeyframeAtPlayhead: authoring GSAP's 0.5s
+    // default here would collapse a duration-less arc's window on drag.
+    const tweenDuration = resolveEditableTweenDuration(anim, selection);
     if (tweenStart === null || tweenDuration <= 0 || keyframes.length < 2) return;
     const temporalKeyframes = buildTemporalArcKeyframes(anim, pct, { x: newX, y: newY });
     await callbacks.commitMutation(

packages/studio/src/hooks/useEnableKeyframes.test.ts

@@ -108,6 +108,19 @@ describe("isPlayheadWithinTween", () => {
   it("does not block when the start can't be resolved", () => {
     expect(isPlayheadWithinTween(anim({ position: "+=1" }), 99)).toBe(true);
   });
+
+  // The toolbar's "extends animation" tooltip has to agree with what the edit
+  // paths do. Those span a duration-less tween across its clip, so answering
+  // from GSAP's 0.5s default reported the playhead outside a window the click
+  // then treated as clip-wide.
+  it("spans the clip for a duration-less tween when given the selection", () => {
+    const durationless = anim({ position: 0 });
+    const selection = { dataAttributes: { duration: "16" } } as unknown as DomEditSelection;
+
+    expect(isPlayheadWithinTween(durationless, 5)).toBe(false);
+    expect(isPlayheadWithinTween(durationless, 5, selection)).toBe(true);
+    expect(isPlayheadWithinTween(durationless, 20, selection)).toBe(false);
+  });
 });
 
 describe("buildExtendedKeyframes", () => {

packages/studio/src/hooks/useEnableKeyframes.ts

@@ -77,11 +77,22 @@ export function animatedProps(anim: GsapAnimation | null): string[] {
  * Whether the playhead sits inside an animation's tween range. When the tween's
  * start can't be resolved we don't block (the percentage falls back to clip range,
  * preserving prior behavior for elements without explicit timing).
+ *
+ * Pass the selection whenever the caller has one: a duration-less tween spans
+ * its clip, and answering from GSAP's 0.5s default reports the playhead outside
+ * a window the edit paths treat as clip-wide.
  */
-export function isPlayheadWithinTween(anim: GsapAnimation, currentTime: number): boolean {
+export function isPlayheadWithinTween(
+  anim: GsapAnimation,
+  currentTime: number,
+  selection?: DomEditSelection | null,
+): boolean {
   const start = resolveTweenStart(anim);
   if (start === null) return true;
-  return isTimeWithinTween(currentTime, start, resolveTweenDuration(anim));
+  const duration = selection
+    ? resolveEditableTweenDuration(anim, selection)
+    : resolveTweenDuration(anim);
+  return isTimeWithinTween(currentTime, start, duration);
 }
 
 /**