feat(buzz-persona): define portable Agent Skill content

[wolfyy970]

Summary

A Skill selected for an agent should still be the same Skill when that agent runs somewhere else, not whichever same-named folder happens to exist on the new machine.

This gives buzz-persona one runtime-neutral representation for a complete Agent Skills directory:

• exact bytes, including scripts, empty files, binary assets, and executable intent
• spec-valid metadata and stable content digests
• portable path validation and an exact review inventory
• allowed-tools shown as an untrusted request, never a permission

It also exposes a validated SKILL.md parser and per-Skill validation, digest, and inspection APIs that #5301 can use without treating a name or local path as portable identity.

Scope

No archive, persistence, installation, activation, or permission grant. Those belong in later layers.

Testing

• just ci
• adversarial tests for path handling, Unicode, identity, size limits, metadata, and binary content

Related

• feat(agent): per-agent skill allowlist + Skill selection UI #5301
• Agent Snapshot v2: reviewable Skills and tool requirements #5267

[wolfyy970]

I have restacked this onto current main. It now owns only exact portable Skill content and shared parsing; installation and activation remain separate.

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 9063b81164

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[wolfyy970]

@wpfleger96, this gives #4485 a shared, exact Skill content model without adding installation or activation authority. Could you review that boundary when you have a moment?