fix: sanitize velocity to prevent instant snap on Reanimated v4+

[ahmadaccino]

Summary

Fixes #2470 — no smooth animation when the bottom sheet snaps back to its initial position on Reanimated v4 + Gesture Handler v2.

Root Cause

Reanimated v4 + Gesture Handler v2 can report an excessively high velocityY whose direction is opposite to the snap target. When this velocity is passed directly to withSpring, the spring overshoots and resolves in a single frame — producing an instant snap with no visible animation.

Fix

Two guards are applied to the velocity inside animateToPosition before it reaches withSpring:

1. Clamp the absolute velocity to ±500 — prevents absurdly high values from producing jarring or invisible animations.
2. Zero the velocity when it opposes the snap direction — if the sheet needs to snap up but velocity points down (or vice versa), velocity is set to 0 so the spring does not fight the target.

Why this is safe for all Reanimated versions

• The guards live in animateToPosition, the single entry point for all snap animations.
• Large opposing velocities are never desirable for a snap animation regardless of Reanimated version.
• On Reanimated v2/v3 where velocity is correctly reported, it is typically already aligned with the snap direction (passes through unchanged) or small enough to be within the 500 cap.
• Programmatic calls (no gesture) pass velocity = 0 by default and are completely unaffected.

Related

• Issue: [Bug]: No smooth animation when returning to the initial position #2470
• Community-validated patch by @jluisrojas confirming this approach resolves the bug.
• Confirmed across iOS with Reanimated v4 + Gesture Handler v2 + Expo 54.