Reduce meniscus-driven wall climbing in SPH update shader

[Testtesttestestes]

Motivation

• Meniscus and wall-contact behavior was pulling particles up vertical walls at low fill levels, producing an unwanted auto-fountain effect.

Description

• Decrease effective contact layer thickness by changing wallContactThickness() to return max(dp * 0.7, 0.05); to reduce how easily particles stick to walls in src/sph/update.frag.
• Add a sideWallFactor (based on abs(normalLocal.x)) and use it to scale tangential wall viscosity (sideTangentialScale) and wall pressure response (sidePressureScale) to weaken adhesion on near-vertical wall segments.
• Reduce the shared tangential "cohesive slip" contribution by scaling it with u_wave_amplitude * 0.35, so container motion no longer amplifies the wall-climb behavior.

Testing

• Ran npm run build which completed successfully.
• Launched the dev server and captured an automated Playwright screenshot after loading http://127.0.0.1:4173/, which confirmed the reduced wall-climb behavior.

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Codex Task