Add MLite skills foundation

[ISEEKYAN]

Summary

Adds an agent-agnostic MLite skills foundation under experimental/lite/skills. Skills are organized like Python modules, use a delimited schema block for retrieval, and use Python-like pseudocode bodies with explicit inputs, outputs, calls, and exits.

Contents

• Defines the skills file layout, schema contract, module naming rules, and lint expectations.
• Adds foundational skills for reference selection, precision alignment, end-to-end precision evidence, proxy task construction, threshold review, and skill linting.
• Adds primitive skills for parallel, module, and optimizer primitives, including TP, EP, PP, CP, DDP, FSDP, DistOpt, MoE, and GQA.
• Adds model composition, application, performance, and insight skills.

Validation

• git diff --check HEAD -- experimental/lite/skills
• Verified each skill has exactly one schema marker pair.
• Verified schema names map to file paths.
• Verified the root skills index covers every schema name.

Notes

This change adds documentation-style operational contracts only. It does not modify runtime, model, primitive, or training code.