Module rendering/post-processing/bloom/bloom.tsl

Bloom pyramid TSL factories — NodeMaterial counterparts to the three GLSL3 shaders in shaders.ts.

Shared pattern: each is a fullscreen pass that reads uInput with a small 4-tap kernel, writes a vec4 RGB output. Differences:

• threshold: 2x2 box downsample + soft-knee threshold gate.
• downsample: 2x2 box downsample (no threshold).
• upsample: 4-tap tent filter + center sample, blended additively onto the destination mip via NodeMaterial.blending.