Phase 4 (brought forward before the mixed-mode boundary). digitalgate-sweep
proves the engine handles 38/38 gallery digital examples: every one builds,
resolves every LED, and never oscillates. Tightened isAllDigital to also require
at least one logic gate, so a degenerate analog {source, resistor, LED} circuit
stays on ngspice rather than being claimed by the digital path. Flipped
digitalGatesEnabled() default to ON (override with ?digitalgates=off).
Full frontend suite 2120 pass / 5 fail — the 5 are the same pre-existing
unrelated failures (ngspice node-path, attiny85 arduino-cli, component-to-spice
catalog); the default flip adds no new breakage and examples-digital +
circuit-simulation-service stay green.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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