D115 — Footprint check against trusted datasheet references

Decision

The footprint check (issue #5) compares a board's footprints with references: records made from a datasheet (JSON, or the manufacturer's .kicad_mod, with document, revision and page), used only when the reference's brand is on an explicit trusted list. The pattern is aligned by translation and quarter-turn rotation, mirrored only as the footprint's side requires, then pad numbers, positions, sizes, drills and types are compared; every difference is an error. route --footprint-refs runs it before routing and stops on an error unless --footprint-warn-only. Read-only

Alternatives

Reading datasheet PDFs (a drawing is not data, and an extracted number would itself need checking); fetching land patterns from the network or from a vendor API (an unpinned, unvouched source); a built-in list of trusted brands applied silently (whose datasheets to believe is the user's call; a starting list is shipped to copy); comparing courtyard, silkscreen, paste or mask; treating an untrusted reference as a verdict

Reason

The issue asks for a check against datasheet footprints with a trusted list of brands. What can be done reliably and offline is to compare with a record someone made from the datasheet and to say whose word that record rests on; an untrusted or missing reference is reported as such, never as "fine" (doc 05 §43)