feat(labels): estate label tooling + auto-triage for new issues

Ships the canonical label set and the classifier that labels newly-filed
issues. Additive only: it never removes a label, never overrides a human's
classification, stays silent when unsure, and never fails an issue.

Also adds this repo's two new workflows to .github/workflows/actions.lock as
'[]'. That lock is keyed by workflow path and refuses any workflow it does not
list -- a startup_failure, which produces no check run and is therefore silent.
`gh actions-lock` cannot add these: it records action versions, and both
workflows deliberately use no actions.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: hyperpolymath