Promote stable MCP Description 0.8 packages

[ObjectIsAdvantag]

Summary

• promote @mcpdesc/validator from 0.12.0-rc.1 to 0.12.0 without runtime changes
• promote @mcpdesc/core from 0.11.0-rc.1 to 0.11.0 without API or behavior changes
• pin core exactly to @mcpdesc/validator@0.12.0
• prepare validator-first publication under the latest npm dist-tag

Validation

• npm run check
• npm run release:plan -- --package both --channel latest --require-specification-tag v0.8.0
• public specification tag v0.8.0 resolves to reviewed commit 918158019a3d15354302531b3b3ab06e8491bbad
• downstream candidate validation passed in mcpcontract and mcptoolkit-editor

Release order

1. @mcpdesc/validator@0.12.0 (validator-v0.12.0)
2. @mcpdesc/core@0.11.0 (v0.11.0)

Both packages will use the latest npm dist-tag.

AI assistance

GitHub Copilot assisted with release preparation, validation, and workflow execution. The maintainer reviewed the changes and remains accountable for the result.