platform: split nvbandwidth SAT into per-socket + all-GPU passes

On multi-socket systems, run the NVIDIA bandwidth diagnostic once per
CPU socket before the all-GPU pass, so a crash confined to the all-GPU
run (with clean per-socket passes preceding it) isolates a cross-socket
peer-to-peer fault instead of leaving it conflated with a general
GPU/PCIe issue. Single-socket systems keep the original one-pass shape.

Also expand the support-bundle README with reference notes distilled
from a real analysis pass (BMC clock drift, "0/empty" tool output
meaning absent hardware rather than a fault, timestamp-matching before
assigning causality, and a normal-power-cycle SEL signature), plus a
step-by-step recipe for diagnosing an unexpected reboot/crash during a
specific test.

.gitignore

@@ -3,3 +3,4 @@
 dist/
 build-cache/
 audit/bee
+audit/.tmp/