Two independent defects, both visible as "the NTC reports the wrong
temperature" (issue #233).
1. The part built its divider against a hard-coded 5 V rail, while the SPICE
path used the board's real rail. They only agreed on AVR. On a 3.3 V board
the injected node sat above the ADC's full scale: the slider at 25 C read
~1.4 C, and every slider value below ~11 C saturated to the same number, so
-40, 0 and 10 C were indistinguishable. The rail now comes from the board
(analogRailVolts), matching setAdcVoltage's own AVR/RP2040/ESP32 split.
2. The divider convention was corrected in 608c2538 (VCC -> R_pull -> OUT ->
R_NTC -> GND) but data/examples.ts was not updated with it, so three of the
four bundled NTC sketches still decoded the OTHER topology. Their readings
came out mirrored about 25 C: the uno-ntc example printed -3.42 C with the
slider at 60 C - the exact symptom dd22bcfe had recorded as the bug. Fixed
in uno-ntc, pico-ntc and attiny85-ntc-sensor; examples-circuits.ts was
already right.
The sibling analog sensors (gas, flame, heart-beat, sound) map their sliders
0..1023 onto the same hard-coded 5 V and will saturate the same way on 3.3 V
boards. Left alone here: that is not what #233 reports, and each one needs its
examples re-checked before changing.
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