Fix arm swing accumulation and stabilize hand grips

[a-baran-orhan]

What changed

• make procedural contralateral arm swing idempotent across render frames
• add a deterministic overhand contact frame for bar-gripping wrists
• apply wrist orientation after positional grip IK and before finger wrapping
• add regression coverage for repeated-frame stability, wrist anchoring, and grip orientation

Why

The forward-lunge left shoulder accumulated the procedural swing correction every frame, causing an uncontrolled spin. Bar movements constrained only wrist position, leaving wrist and palm orientation underdetermined and producing poor-looking pull-ups, hangs, and other hand-supported movements.

Impact

Forward lunges keep stable, natural arm swing. Pull-ups and other bar-grip movements now use a consistent contact-aware hand orientation without moving the wrist away from its IK anchor. This establishes an orientation-aware contact layer for future handles, rails, and two-handed props.

Validation

• npm test -- --run — 246 tests passed
• npm run build — production build passed
• visual checks of forward lunge and pull-up
• no browser console warnings or errors

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Project	Deployment	Actions	Updated (UTC)
posecode	Ready	Preview, Comment	Jul 12, 2026 8:45pm