Refactor falling berries to use WebGPU compute shaders

[ford442]

Migrated the falling berry physics and transformation updates in src/foliage/berries.ts from a CPU-side loop managing an instanceMatrix to a native WebGPU ComputeNode. Used StorageInstancedBufferAttribute to track position and velocity. Retained a lightweight CPU proxy solely for resolving player collection collisions, drastically reducing CPU Float32Array write overhead and eliminating the O(N) .setMatrixAt calls.

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PR created automatically by Jules for task 1120028224226334643 started by @ford442

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