0.5.9 — a heater test you can actually read

The heater test was five seconds. That was decided before there was a heater to test, and it is not long enough: resistor bodies have real thermal mass, and a correctly wired heater felt like a dead one.

Changed

• Choose the duration — 15 seconds, 1 minute, or 2 minutes. Default is a minute. The hard cap is now two minutes.
• The test measures itself. The BME280 is already on the glass, so it is read either side of the pulse and the card reports the temperature rise. "Does it feel warm?" is a poor question when the resistors are inside a dome or behind glass.

A small reading is reported, not judged: where the sensor sits relative to the heat decides whether it can see a rise at all, so the card says so and tells you to feel the resistors before assuming a fault.

Unchanged

The pin is still switched off in a finally block, so a dropped connection or a crash mid-test still ends with the heater off.