Remove docs/SPEC.md and update references

[fullstackjam]

What does this PR do?

Removes the docs/SPEC.md specification document and updates all references to it in the codebase.

Why?

The SPEC.md file contained detailed v1.0 CLI specification and design decisions that are no longer needed as active documentation. References in CLAUDE.md, CONTRIBUTING.md, and CHANGELOG.md have been updated to remove links to this file.

Testing

• go vet ./... passes
• No code changes; documentation-only removal

Notes for reviewer

This is a documentation cleanup change. The specification details previously in SPEC.md are no longer referenced in the active developer documentation. All cross-references have been removed from:

• CLAUDE.md (removed reference to SPEC.md for protocol/data model)
• CONTRIBUTING.md (removed reference to SPEC.md for CLI surface)
• CHANGELOG.md (removed reference to SPEC.md)

No functional code changes are included.

https://claude.ai/code/session_01Re7sPY24JZy5UDwUqd7S39

[github-actions]

👋 Thanks for opening this pull request!

Before merging:

• Code follows existing patterns in the codebase
• go build ./... and go vet ./... pass
• Commit message is clear and descriptive

@fullstackjam will review this soon. Thanks for contributing! 🚀

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!