fix(sdk): moveElement survives GSAP animation per-axis via runtime delta translate (#1875)

* fix(sdk): moveElement survives GSAP animation per-axis via runtime delta translate

A committed moveElement wrote data-x/data-y but nothing rendered them:
hosts shimmed CSS translate, which GSAP folds into the cached transform
at first parse and then discards on the animated axis at every seek —
dragging an animated element kept only the un-animated axis.

Spike-proven on GSAP 3.15: a translate set AFTER GSAP's first parse is
never read, folded, or cleared across seeks and composes natively with
the animated transform. So:

- moveElement captures the pre-edit baseline once (data-hf-edit-base-x/y)
- the runtime (new core runtime/positionEdits.ts, applied at timeline
  bind — after GSAP parse) renders translate = (data-x − base), a pure
  delta that composes with GSAP tweens, tl.set positions, and CSS alike
- applyDraft now drives the drag preview through the same translate
  channel (the --hf-studio-dx/dy vars had no consumer outside authored
  Studio bridges), and commitPreview mirrors the committed move onto
  the live element so it holds without an srcdoc reload

Acceptance: packages/engine/scripts/test-runtime-position-edits-browser.ts
(real Chrome + GSAP + runtime IIFE, no Studio shell) — X-animated,
Y-animated, and static elements hold both edited axes across the full
seek range. New subpath export @hyperframes/core/runtime/position-edits.

Known limitation (documented): a tween created lazily at runtime that
first-parses a marked element after apply folds the edit.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(sdk): harden position-edit rendering and the drag draft channel

Fixes six issues from adversarial review of the moveElement stack:

- Runtime: apply position edits at init as well as at timeline bind, so
  committed moves render in compositions with no usable GSAP timeline
  (CSS/WAAPI-animated or fully static) — previously the apply was
  unreachable outside the boundDuration > 0 bind branch and the edit
  silently vanished from reloads and renders.
- Runtime: guard bind-path re-apply against post-fold double-apply — if
  the previously written translate was consumed externally (a lazily
  created tween folding it into GSAP's cached transform), skip instead
  of re-setting it on top ({force} escape hatch for editor commits).
- Adapter: stop writing the --hf-studio-dx/dy custom properties during
  drags — compositions with the documented var-consuming drag-bridge
  CSS moved by twice the pointer delta (var transform + new inline
  translate). The inline translate is now the only draft channel;
  deltas accumulate in adapter fields. Docs updated to match.
- Adapter: switching applyDraft to a new id reverts the abandoned
  element's draft translate instead of leaving it displaced with no op.
- Adapter: cancelPreview restores the raw inline translate (removing it
  when there was none), so a stylesheet-authored translate is never
  promoted to a permanent inline style.
- Adapter: commitPreview reverts the draft and clears state when
  dispatch throws, instead of leaving the element shifted by an
  uncommitted draft.

Cleanups: reuse readCurrentTranslate from the core module (was a
verbatim copy), drop the dead __hfApplyPositionEdits window hook.
Browser acceptance test now also covers the GSAP-free composition path.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(core): prime GSAP transform cache before position-edit apply; add fold-loss telemetry

Addresses PR #1875 review feedback (Rames, Miga):

- Prime the element's GSAP transform parse (gsap.getProperty) before the
  first translate apply — positioned tl.set()s and tweens that first
  RENDER after the apply now reuse the cache instead of folding the edit.
  This closes the lazy-first-parse fold-loss for any page where GSAP is
  loaded at apply time; the residual limitation is GSAP itself loading
  after the apply. Proven by the extended browser acceptance test.
- Emit position_edit_fold_skipped analytics at the fold-guard skip site
  so the residual degradation is observable instead of silent.
- Browser acceptance test: add a both-axis-animated element (the shape
  that originated the per-axis loss) and a positioned tl.set() element,
  asserted across the full seek range.
- Simplify the num() null guard (review nit).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

docs/sdk/guides/canvas-integration.mdx

@@ -86,7 +86,7 @@ iframeDoc.addEventListener("click", (e) => {
 
 The draft loop keeps the model clean during a drag. The SDK is **not** in the 60fps path — you call `preview.applyDraft` on every `pointermove` and `preview.commitPreview` once on `pointerup`. The model sees exactly one `moveElement` op per drag, rather than hundreds.
 
-`applyDraft` writes CSS custom properties (`--hf-studio-dx`, `--hf-studio-dy`) directly onto the target element inside the iframe. The composition's CSS uses these vars to translate the element visually. Nothing in the SDK model changes.
+`applyDraft` sets the element's CSS `translate` directly inside the iframe — the pre-drag value composed with the accumulated delta — so the drag is visible in any composition without composition-side CSS, and works on GSAP-animated elements (a `translate` set after GSAP's first parse composes with the animated transform instead of being overwritten). Nothing in the SDK model changes. `cancelPreview` restores the pre-drag translate; `commitPreview` derives one `moveElement` op and mirrors the committed position onto the live element.
 
 ```typescript
 let dragging = false;