Add portable Read the Code agent skill

[kvkenyon]

Summary

• add a canonical portable Agent Skills package for the complete read-the-code-axi review lifecycle
• document direct source and packed-package installation paths for common coding-agent clients
• ship the skill in the npm tarball and validate its frontmatter, CLI help contract, links, and secret-safe examples
• extend the packed smoke test through exact open, feedback polling, approval, stale-head invalidation, export, and end

Why

Coding agents should be able to request durable local human review without memorizing CLI details or opening a pull request. The skill makes revision binding, cursor continuity, untrusted feedback handling, capability secrecy, recovery, and approval boundaries part of the public product contract.

Impact

The CLI and protocol remain unchanged. Consumers can install skills/read-the-code through standard Agent Skills discovery paths, including directly from the packed npm product.

Validation

• npm run check
• npm run test:e2e
• Agent Skills quick_validate.py skills/read-the-code