D108 — KiCad 10 defaults and legacy migration precedence for rules

Decision

Seed supported KiCad 10 defaults, retain missing project keys and explicit zeros, and follow native legacy migration precedence: exact legacy setup triggers suppress project board settings, while legacy net classes independently replace project classes/assignments

Alternatives

Zero minimums for partial projects; unconditional project-over-legacy overlays; suppression whenever any setup exists

Reason

KiCad's constructor sets track/via minimums to 0.2/0.5 mm. BOARD::SetProject skips project board-settings loading only after parser-marked legacy design settings and independently migrates root net classes. Native controls and consumer-visible unit tests distinguish rule triggers from local mask fields and verify legal written widths (doc 08 §3.1)