Extends the over-voltage rule to the two cases the previous slice deferred:
- Boards (ESP32 / Pico / Arduino / ...): a board's supply pins all collapse to
the self-driven vcc_rail net, so an external source on them makes the .op
singular rather than readable. Added a graph-based check (runs before the
solve): if a power source is wired to a board supply pin and its nominal
voltage exceeds that pin's rating, warn. Threaded boardKind into
BoardForSpice so the verifier can look up the board rating.
- Electrolytic capacitors: new `voltage` rating property (select, default 25V,
on capacitor-electrolytic + cap-elec-* presets, via component-overrides +
regenerated metadata). The verifier reads the DC voltage across the +/- pins
and warns on over-voltage (vent/burst) and on reverse polarity (a polarized
cap wired backwards). Defaults to 25V when the property is unset.
Tests: 9V battery -> ESP32 VIN warns, 1.5V doesn't; 24V across a 16V cap warns,
5V across a 25V cap doesn't; reverse-biased cap warns. All real-ngspice.
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