fix(FallingText): stop the update loop on cleanup

[noron12234]

Changing a running FallingText's gravity recreates its effect, but the old updateLoop continues to schedule requestAnimationFrame callbacks. Unmounting stops Matter's runner and renderer while leaving that separate loop updating the old word elements and cleared engine.

This captures the latest frame ID and cancels it before the existing teardown, across all four JS/TS and CSS/Tailwind variants.

Reproduction in Chrome with a small Vite harness importing the actual component files: wrap requestAnimationFrame/cancelAnimationFrame to count pending callbacks named updateLoop; render FallingText with trigger="auto"; change gravity from 1 to 1.2 to 0.8, allowing effects to run between renders; unmount and observe for another 150 ms. Repeat for each variant, with and without React StrictMode.

Before: pending updateLoop callbacks grow from 1 to 2 to 3, and all three remain after unmount. Each case still executes 21 to 30 callbacks during the subsequent 150 ms observation.
After: pending callbacks stay at 1 across prop changes, become 0 on unmount, and no further updateLoop callback executes.

Validation:

• All eight browser cases pass in desktop Chrome and a 390 x 844 viewport.
• No captured runtime errors in the harness.
• ESLint passes for both JS variants; Prettier passes for all four variants.
• Targeted TypeScript check passes for both TS variants with target ES2020, DOM/DOM.Iterable, react-jsx, node module resolution, esModuleInterop, and skipLibCheck.

The browser harness is local verification, not a new project test dependency. This is scoped to the component's separate animation loop; it does not change physics timing or other resource ownership. Developed with Codex assistance.