918-line design doc covering all three capabilities from m/paliad#61:
authoring, multi-axis sharing, admin-promotion to global.
Load-bearing premise correction: the issue body claims `paliad.checklists`
is an existing table that gets new columns. It is NOT — checklists today
are static Go data in `internal/checklists/templates.go`. Design
introduces `paliad.checklists` from scratch and keeps the static catalog
as a parallel source via a hybrid catalog read layer.
Schema (mig 112): `paliad.checklists` (owner + visibility enum), `paliad.checklist_shares`
(polymorphic recipient: user/office/partner_unit/project),
`paliad.can_see_checklist` predicate, `paliad.checklist_instances.template_snapshot`
column for instance integrity under template edits.
12 decisions ledgered, all defaulted to (R) per task brief (no AskUserQuestion).
Three slices (A foundation, B sharing+promotion, C gallery+backfill).