Chef iQ CQ60: mask not-measured probe sentinels as None

[ITSpecialist111]

Summary

When a Chef iQ CQ60 ring sensor has nothing touching it (probe only partially inserted, exposed to ambient air, or a broken internal wire) the firmware emits a "not-measured" sentinel rather than a real reading:

Field	Type	Sentinel
meat / tip / probe 1 / probe 2 / ambient	H (uint16, °C × 10)	0x7FFB (and any value >= 0x7FF0)
probe 3	B (uint8, °C)	0xFE / 0xFF

The current parser divides those through unchanged, which surfaces in Home Assistant as 3276.3 °C on the affected entities. That:

• trips the temperature device-class sanity limits and pollutes recorder/statistics graphs,
• fires any user automations with a numeric_state: above: 60 trigger the moment the device wakes,
• makes a "doneness" template entity flip into "well done" before any food is even on the probe.

I observed this on a real CQ60 (manufacturer ID 0x05CD, MAC D9:38:36:2E:33:73) — every wake cycle where only the meat probe was inserted produced meat = 20.1, tip = 20.1, probe_1 = probe_2 = ambient = 3276.3.

Change

Add a tiny _decode_temp(raw) helper plus a TEMP_SENTINEL_MIN = 0x7FF0 constant, and route every H-encoded ring temperature through it. The 8-bit probe_3 is masked separately (< 0xFE). Any sentinel becomes None, so the resulting HA entity reports as unavailable instead of an absurd value.

Battery scaling is deliberately unchanged in this PR — the existing test asserts battery == 99 from a raw 0x63 byte, and I haven't been able to confirm from public docs whether the firmware reports a 0–100 percentage or a raw 0–255 byte (my device emits 0xCC / 204 when freshly charged, which would suggest the latter). Happy to follow up in a separate PR with a scaling change once that's nailed down — I didn't want to entangle it with the (clearer) sentinel correctness fix.

Tests

• The existing test_chefiq_cq60 is unchanged and still passes — the sample packet has no sentinel values.
• A new test_chefiq_cq60_sentinels case feeds an otherwise-identical packet with every ring temperature set to its sentinel and asserts that all six temperature fields decode to None while battery / MAC / type still populate normally.

Risk

Zero behaviour change for any payload that doesn't contain a sentinel. The masking only affects values that the receiving HA temperature sensor would have rejected (or graphed as a 3,000 °C spike) anyway.