id	2607191918
title	Deduplicate isClaimed between internal/schema and requiredstructure
status	✅
model	haiku
summary	internal/rules/requiredstructure/rule.go carries a byte-for-byte copy of internal/schema/validate.go's isClaimed helper, despite already importing internal/schema. Flagged by the 2026-07-19 audit.

Deduplicate isClaimed between internal/schema and requiredstructure

Goal

Remove the duplicated isClaimed helper so the claimed-range check has one implementation.

The 2026-07-19 audit (see the audit log) found this duplication:

requiredstructure/rule.go carries a copy of schema/validate.go's isClaimed helper.
Its comment reads "Mirrors internal/schema/validate.go's isClaimed for the identical pattern" instead of reusing it.
requiredstructure/rule.go already imports internal/schema. This isn't an import-cycle workaround — it's a plain copy.
go.md's refactor-moves section names this exact shape: "Lift a shared dependency up to an interface... once two rules needed the same shape."

Export the helper from internal/schema (e.g. schema.IsClaimed) or move it to a small shared set-helper both packages can import without creating a cycle — check internal/schema's existing dependency direction against requiredstructure first, since requiredstructure importing schema already establishes the direction that must hold.
Delete requiredstructure/rule.go's private copy and call the shared helper instead.
Keep or adapt the existing test coverage for both call sites; do not remove test coverage in the move.
go build ./... passes.
go test ./internal/schema/... ./internal/rules/requiredstructure/... passes.