[Architecture] Semantic versioning for lessons and protocol

[Ikalus1988]

Task

Define versioning scheme for lessons and the SKP protocol.

Acceptance Criteria

• Lessons: semver based on content changes (major=breaking, minor=addition, patch=fix)
• Protocol: semver for misaka-protocol.json schema
• Changelog: auto-generated from lesson version changes
• Backward compatibility: old agents can read new lessons
• Migration guide for breaking changes

Why it matters

Versioning enables federation — nodes need to know if they can read each other's lessons.

Difficulty

🔴 Ring-4 — versioning design.

---

This repo is using Opire - what does it mean? 👇

💵 Everyone can add rewards for this issue commenting /reward 100 (replace 100 with the amount).
🕵️‍♂️ If someone starts working on this issue to earn the rewards, they can comment /try to let everyone know!
🙌 And when they open the PR, they can comment /claim #327 either in the PR description or in a PR's comment.

🪙 Also, everyone can tip any user commenting /tip 20 @Ikalus1988 (replace 20 with the amount, and @Ikalus1988 with the user to tip).

📖 If you want to learn more, check out our documentation.