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/studio/src/components/editor/gsapAnimationConstants.ts

@@ -37,6 +37,7 @@ export const PROP_LABELS: Record<string, string> = {
   letterSpacing: "Tracking",
   skewX: "Skew X",
   skewY: "Skew Y",
+  innerText: "Counter Value",
 };
 
 export const PROP_UNITS: Record<string, string> = {
@@ -65,6 +66,7 @@ export const PROP_TOOLTIPS: Record<string, string> = {
   height: "Element height",
   autoAlpha: "Like opacity but hides element completely at 0",
   visibility: "Show or hide the element",
+  innerText: "End value for a number roll-up (the number it counts up/down to)",
 };
 
 export const EASE_LABELS: Record<string, string> = {
@@ -154,6 +156,7 @@ export const PROP_CONSTRAINTS: Record<string, { min?: number; max?: number; step
   y: { step: 1 },
   fontSize: { min: 1, step: 1 },
   letterSpacing: { step: 0.1 },
+  innerText: { step: 1 },
 };
 
 export function clampPropertyValue(prop: string, value: number): number {