feat: TSL skills (tsl-fundamentals, tsl-patterns)

[devallibus]

Context

Follow-up from #56 (TSL support). The shaderbase-skills/ directory needs TSL-specific skills for AI agents working with Three Shading Language shaders.

Skills to create

tsl-fundamentals

• TSL node API basics (color, float, vec3, uv, time, etc.)
• Node composition patterns (.mul(), .add(), .mix())
• Common nodes: sin, cos, fract, step, smoothstep
• NodeMaterial setup and colorNode / positionNode assignment
• Import patterns (three/tsl, three/webgpu)
• The createMaterial() contract

tsl-patterns

• Advanced TSL recipes: noise, SDF, procedural textures
• Animated patterns using time node
• Color manipulation and blending
• Geometry displacement via positionNode

Update shaderbase-manifest skill

• Document TSL manifest fields (language: "tsl", tslEntry)
• Show TSL manifest examples alongside GLSL
• Document the node-material compatibility value

Reference

• Three.js TSL docs: https://threejs.org/docs/#api/en/nodes/core/Node
• Existing TSL shader in corpus: shaders/tsl-gradient-wave/