promote --topic declares current documents in the catalog (DR-020); three RFC drafts; 0.8.1

[emafriedrich]

Promoting a spec set its status but never declared it under current: in the domain's catalog entry, so the domain's CONTEXT.md did not list it as current truth.

• promote <ID> --by <human> --topic <name> now declares any document that becomes current in its domain's current:, in the same operation. It refuses a name held by another document, can be re-run on a document that is already current, and keeps an implemented spec implemented. Without --topic it promotes and says the document is not declared.
• --topic on an RFC is refused instead of silently ignored.
• The validator warns, without failing, on a current or implemented spec declared in no domain.
• DR-020 (draft, agent-drafted) records the rule; KDE-SPEC-001 and HANDBOOK updated; 4 new tests; version 0.8.1, installer and curl lines point at v0.8.1.

Three RFC drafts for review by the maintainer or the community, no choice made:

• KDE-RFC-016: a ticket named in a PR must be cited by some knowledge document, or the PR says why not.
• KDE-RFC-017: whether the task artifact earns its place, since field use never wrote one.
• KDE-RFC-018: where a decision that binds several repositories lives.

npm test 70/70, knowledge:check ok (11 pre-existing staleness warnings on accepted RFCs against KDE-SPEC-001).

After merge: promote DR-020 (npm run knowledge -- promote DR-020 --by <human> --topic current-anchor) and push tag v0.8.1.