add Confidential Computing readiness check + collect nvidia-smi conf-compute -q

New read-only "Check" step reports whether this server can run NVIDIA
Confidential Computing: CPU TEE support (Intel TDX / AMD SEV-SNP, via
dmesg and kvm_amd sysfs params) and GPU firmware CC capability (via
`nvidia-smi conf-compute -q`). Also collect that command's output into
the techdump export bundle.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

audit/internal/platform/techdump.go

@@ -38,6 +38,7 @@ var techDumpNvidiaCommands = []struct {
 }{
 	{Name: "nvidia-smi", Args: []string{"-q"}, File: "nvidia-smi-q.txt"},
 	{Name: "nvidia-smi", Args: []string{"--query-gpu=index,pci.bus_id,serial,vbios_version,temperature.gpu,power.draw,ecc.errors.uncorrected.aggregate.total,ecc.errors.corrected.aggregate.total,clocks_throttle_reasons.hw_slowdown", "--format=csv,noheader,nounits"}, File: "nvidia-smi-query.csv"},
+	{Name: "nvidia-smi", Args: []string{"conf-compute", "-q"}, File: "nvidia-smi-conf-compute-q.txt"},
 }
 
 type lsblkDumpRoot struct {