fix(studio): author every new tween against one element

U3 fixed "add keyframe at playhead" widening a write to every sibling
sharing a class, but wired writeTargetSelector into only two paths. The
same bug was still reachable from the add-animation button, drag, resize,
rotate, gesture recording, and the property panel: each derived its target
from selectorFromSelection, which hands back a bare class for an id-less
element, so one edit authored a tween over all five siblings and the
timeline collapsed their rows into one.

Route every path that authors a NEW tween through the existing ladder:

- ensureElementAddressable now accepts selection.selector only when it
  addresses exactly one element, so the id-minting fallback right below it
  (previously unreachable whenever any selector was present) does the work.
- gsapDragCommit's five new-tween branches go through one newTweenTarget
  helper; instant patches reuse the written target so the runtime moves the
  element the source write names.
- useGestureCommit and useAnimatedPropertyCommit keep the existing selector
  for matching/retargeting and author new tweens with a separate write
  selector.

Retargets of an EXISTING tween are deliberately untouched: they keep
anim.targetSelector, so a tween aimed at a whole group stays aimed at it.

Narrowing the write alone regressed idempotency, verified by test: the
"is there already a write for this element" lookups matched targetSelector
by string, so the next nudge missed the write it had just made and appended
a second, conflicting one. The read half now falls back to the live DOM
(tweenTargetsElement, same contract as getAnimationsForElement), which also
still matches a deliberate group tween.

Tests reproduce each site through a real writer, re-parse with the real
parser, and resolve through resolveSelectorElementIds (what feeds the
keyframe cache and the lanes), plus pins for the new-tween vs
retarget-existing distinction so a future change cannot collapse the two.

packages/studio/src/hooks/gsapDragStaticSetHelpers.ts

@@ -1,6 +1,6 @@
 import type { GsapAnimation } from "@hyperframes/core/gsap-parser";
 import type { RuntimeTweenChange, SetPatchProps } from "./gsapRuntimePatch";
-import { isInstantHold } from "./gsapShared";
+import { isInstantHold, tweenTargetsElement } from "./gsapShared";
 
 /** The shape of an `update-property` mutation a static-set nudge POSTs. */
 interface UpdatePropertyMutation {
@@ -34,12 +34,13 @@ export function setPatchFromUpdateProperty(
 function findPositionSetAnimation(
   animations: GsapAnimation[],
   selector: string,
+  element?: Element | null,
 ): GsapAnimation | null {
   return (
     animations.find(
       (a) =>
         a.method === "set" &&
-        a.targetSelector === selector &&
+        tweenTargetsElement(a.targetSelector, selector, element) &&
         ("x" in a.properties || "y" in a.properties),
     ) ?? null
   );
@@ -61,12 +62,16 @@ function findPositionSetAnimation(
 export function findExistingPositionWrite(
   animations: GsapAnimation[],
   selector: string,
+  element?: Element | null,
 ): GsapAnimation | null {
-  const set = findPositionSetAnimation(animations, selector);
+  const set = findPositionSetAnimation(animations, selector, element);
   if (set) return set;
   return (
     animations.find(
-      (a) => a.targetSelector === selector && a.propertyGroup === "position" && isInstantHold(a),
+      (a) =>
+        tweenTargetsElement(a.targetSelector, selector, element) &&
+        a.propertyGroup === "position" &&
+        isInstantHold(a),
     ) ?? null
   );
 }
@@ -74,10 +79,14 @@ export function findExistingPositionWrite(
 export function findRotationSetAnimation(
   animations: GsapAnimation[],
   selector: string,
+  element?: Element | null,
 ): GsapAnimation | null {
   return (
     animations.find(
-      (a) => isInstantHold(a) && a.targetSelector === selector && "rotation" in a.properties,
+      (a) =>
+        isInstantHold(a) &&
+        tweenTargetsElement(a.targetSelector, selector, element) &&
+        "rotation" in a.properties,
     ) ?? null
   );
 }
@@ -85,12 +94,13 @@ export function findRotationSetAnimation(
 export function findSizeSetAnimation(
   animations: GsapAnimation[],
   selector: string,
+  element?: Element | null,
 ): GsapAnimation | null {
   return (
     animations.find(
       (a) =>
         isInstantHold(a) &&
-        a.targetSelector === selector &&
+        tweenTargetsElement(a.targetSelector, selector, element) &&
         ("width" in a.properties || "height" in a.properties),
     ) ?? null
   );