Tiny World Render Performance

Keep the renderer single-pass and predictable.

Current renderer contract:

• Default render path is direct except for two explicit render-target systems: the optional pixelation pass (low-res render target + depth/normal-edge fullscreen quad) and the enhanced-water planar reflection pass. The reflection pass renders the scene once from a mirrored camera into tw-water-planar-reflection, hides reflective water during capture, clips below-water geometry, and is disabled in XR / when enhanced water is off. Do not introduce any other always-on post passes (EffectComposer, screen shaders, additional render targets) without explicit approval.
• Cap DPR; do not return to uncapped devicePixelRatio. Dynamic resolution (renderDynamicResolution) is an adaptive multiplier below the user's Resolution slider ceiling: it adjusts effective pixel ratio slowly toward Target FPS and never persists its transient scale.
• Warn on software WebGL renderers (SwiftShader/llvmpipe/softpipe/WARP/etc.) with the dismissible hardware-acceleration banner; many FPS complaints come from browser hardware acceleration being disabled.
• Main WebGL context uses antialias: true; the old smoothing/post pass has been removed.
• Brightness/saturation/contrast are lightweight CSS filters on the WebGL canvas, not shader uniforms.

GPU caches (introduced for low-end GPU + visible-distance scaling):