Update the journal-set doc entry, the CLI diagnostic table, and the
authoring skill, along with the in-app empty-state hint and the var
message comment.
Move the skill to .agents/skills/tttk-authoring and point gen:skill-reference at it. Activate it by symlinking ~/.agents/skills/tttk-authoring to the in-repo copy.
Extend the reference drift guard to cover the skill copy now that it is versioned, and document activation in docs/development.md.