feat(gsap): add innerText support to GSAP inspector for counter animations (#1244)

Adds 'innerText' as a supported GSAP property so number roll-up animations
(count-up from 0 to some value) are visible and editable in the GSAP inspector
panel.

- Add 'innerText' to SUPPORTED_PROPS in gsapConstants.ts
- Add label 'Counter Value', tooltip, and step constraint (1) in
  gsapAnimationConstants.ts

The snap modifier that controls integer rounding is already preserved
verbatim via the EXTRAS_KEYS round-trip, so rounding behavior survives
edits without any additional UI changes.

Closes #1179

packages/core/src/parsers/gsapConstants.ts

@@ -41,6 +41,8 @@ export const SUPPORTED_PROPS = [
   // Filter & Clipping
   "filter",
   "clipPath",
+  // DOM content (number counters, text roll-ups)
+  "innerText",
 ];
 
 export const SUPPORTED_EASES = [