release: v1.20.0 — die temperature as an eighth load source

The eighth load source, and the first one that reads how hot the machine is rather than how busy.

Added

• An eighth load source: die temperature (--load-source temperature, or pick Temperature
  from Other Sources in the menu). Where fan speed is the lagging thermal signal — fans trail
  the work that heated the machine by seconds — this is the leading one: the die responds in
  milliseconds. Read at the same unprivileged tier as every other source (no sudo, no
  entitlement), straight off the performance-core temperature sensors via the shared SMCClient
  that shipped in 1.19.4. The menu shows the hottest sensor, the spread across all of them, and how
  many answered; the menu-bar label shows TMP 72°. Machines where no sensor answers (typically
  VMs) disable the row and fall back to CPU, exactly like fan on a fanless Mac.

  Three things about it are deliberate and worth knowing. The animation follows the hottest
  sensor, not the average — throttling responds to the hottest die, and averaging a loaded core
  cluster against an idle one hides the event worth watching. The scale is absolute (30 °C idle
  → 100 °C flat out) rather than rescaled to your machine's recent range, so a given animation speed
  means the same temperature on every Mac and on every day; the cost is that a Mac which cools well
  never quite reaches the top of the range, which is the honest reading rather than a flattering
  one. And only ~12 cluster sensors are sampled per tick rather than all 102 the chip publishes —
  they carry the same maximum, and the full sweep would have cost about 1% of a core continuously,
  which is not a thing an indicator built to not add load gets to spend.