Two related correctness fixes that make the simulator's realism
match what users actually see.
1. circuitVerifier was running pre-flight against the IDLE circuit
(every pin LOW). A Blink sketch is going to write pin 13 HIGH
eventually — at which point a missing series resistor produces a
~500 mA spike through the diode. But because pre-flight ran with
pin 13 LOW the led-overcurrent rule never fired, and the user
sailed through Run only to see the LED stay mysteriously dark on
the canvas.
The verifier now forces every digital pin connected to a load to
HIGH = vcc, the worst case any well-defined sketch will eventually
impose. The existing rules (led-overcurrent, resistor-overpower,
short-circuit) now fire correctly and the existing
CircuitVerificationModal blocks Run until the user adds a proper
current limiter or chooses Run Anyway.
Pins that are inputs-only (a pull-up + button) get over-driven
here too, but the rules tolerate that — a pull-up at 5 V draws
~0.5 mA, well below all thresholds. A circuit that would actually
fault under HIGH is flagged.
2. LED simulator was crashing visually on non-finite ngspice branch
currents. A degenerate diode (no series R) makes ngspice return
NaN, which fell through 'raw !== undefined && current > 1e-6' as
false and never triggered the digital fallback. Now we check
Number.isFinite(raw) before trusting it — non-finite returns
route to the digital fallback so the LED at least lights visually
when its driver pin is HIGH (the user still sees the verifier
warning that the real-world circuit is wrong, but Run Anyway is
not a black screen).
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