Add experimental RTX 5090 (GDDR7) memory temperature support

Reads the per-module GDDR7 DRAM sensors (FBPA DQR) directly and reports
the hotspot by default; --per-module lists each of the 8 modules.
Adds a per-device decode so the existing GDDR6/6X path is unchanged.

.gitignore

@@ -2,3 +2,11 @@ gddr6
 build/
 *.o
 *.a
+
+# local reverse-engineering probes / scratch tools
+probe_*
+probe5090*
+scan_therm*
+measure_gentle*
+memload*
+!*.md