Previously, the endpoint suppression logic skipped any wire where at least
one endpoint touched a pin, hiding the case where both endpoints are pins
of the same component (a direct pin-to-pin short through the body).
Replace the single endpoint_matches_pin loop with separate start_at_pin /
end_at_pin checks; suppress only when exactly one endpoint is at a pin.
Add regression test to cover this case.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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