T1000-E: Negative temperature values incorrectly displayed due to char signedness

[R6DJO]

Summary

• Fixed incorrect display of negative temperature values in T1000-E sensor variant
• Changed ntc_temp2 array type from char to int8_t

Problem

The ntc_temp2 lookup table in variants/t1000-e/t1000e_sensors.cpp was declared as char, which can be unsigned on some platforms (depending on compiler defaults). This caused negative temperature values (from -30°C to -1°C) to be incorrectly interpreted as large positive values.

Solution

Changed the array declaration from:

static char ntc_temp2[136] = { -30, -29, -28, ... }

to:

static int8_t ntc_temp2[136] = { -30, -29, -28, ... }

This ensures the array is always treated as signed, allowing proper handling of negative temperatures.

Impact

• Fixes temperature readings in cold environments (below 0°C)
• No impact on positive temperature readings
• Single-line change with no API modifications

Test plan

• [*] Compile for T1000-E variant
• [*] Test temperature readings in sub-zero conditions

Fixes #1389

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