Guards
Deterministic pure functions of (events, now) from a closed, versioned
vocabulary (tik.guard). Never effectful: verify must re-evaluate them
identically, offline, years later. Effectful validation lives only in edge
admission checks (CLI porcelain, server ingest), before events are minted.
Design law: facts over flags. A bare boolean guard is a checkbox with
extra steps; tik lint warns. Prefer facts useful downstream — categories
that route branches, artifacts, signed approvals.