With no cycle set the oven reports x.com.samsung.da.desired = 0, and
flatten() published that straight through as target_temp_c. Home
Assistant rejects it against the Number entity's declared 30-270 range
on every publish, which produced 66,899 log errors over three weeks:
Invalid value for number.samsung_oven_setpoint: 0 (range 30.0 - 270.0)
0 is not a 0 degree target, it is the absence of a setpoint, so treat
anything outside the settable band as absent. null lands as unknown on
both the Number and the Setpoint sensor, the way completion_minutes
already reads when the oven is idle. _setpoint applied these bounds on
the write side already; only the read path was missing them.
Adds the first tests for the sample descriptors. One of them pins a
non-obvious asymmetry: the write path snaps to the 5 degree step grid
before bounds-checking, so 29 commits as 30 and 271 as 270, and only 0
is refused outright. The invariant that has to hold is the weaker one,
that every value the write path commits is one flatten() will publish
back, or a write appears to succeed and then reads as unknown.