HyundaiCanada: convert HI/LOW air-temp to resolved unit (fixes 62°C/82°C dropout, issue #30)

[MrL0]

What this does

parseCanadaAirTemp returns the HVAC range bounds for "HI"/"LOW":

if raw == "HI"  { return Temperature(value: Temperature.maximum, units: units) }
if raw == "LOW" { return Temperature(value: Temperature.minimum, units: units) }

But Temperature.maximum/minimum are Fahrenheit constants (62/82 — the Fahrenheit hvacRange), and Temperature.init(value:units:) stores the raw value without conversion. When a Canadian response resolves units to .celsius (top-level "C"), "HI" lands as 82°C and "LOW" as 62°C — impossible cabin temperatures. TemperatureDisplay.isPlausibleForDisplay then rejects them (Celsius must be ≤ 60), so the reading silently disappears. 62°C is the exact artifact documented for issue #30.

Fix: convert the Fahrenheit bound into the resolved unit before storing — matching what Temperature's string initializer already does (Units.fahrenheit.convert(Temperature.maximum, to: units)). A Celsius vehicle now stores ~27.8 °C / 16.7 °C; Fahrenheit is unchanged.

Testing

swift test — 290 tests pass. The conversion itself is covered by the existing Temperature.Units.convert tests; this only changes the unit the HI/LOW bound is stored in. (No Canada-specific parse fixture exists in the suite to assert end-to-end.)

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Drafted with AI assistance; verified locally with swift test.