List and delete spec comments from the protocol server

Hive’s Model Context Protocol server now lets clients read and clean up spec discussions without leaving their tool surface. Two new tools are registered with the protocol server: list_spec_comments returns the comment thread for a visible spec using the same spec reference format as existing spec tools, and delete_spec_comment removes a comment by its identifier, limited to comments authored by the caller. The list tool honors the parent spec’s visibility rules, and the delete tool is flagged as destructive in its tool annotations while reusing the existing author-only ownership check.