Fix SATA discovery, add NVLink bridge detection, add infiniband-diags

- storage: add jsonInt64 dual-format unmarshaler to handle lsblk output
  change in util-linux 2.38 (LOG-SEC/PHY-SEC now emitted as JSON
  integers, not quoted strings); fixes SATA disks invisible on Debian 12
- pcie: detect NVLink bridge mezzanine CX-7 cards (Mellanox x2, no host
  net ifaces, DeviceName contains "NVLINK" in lspci -v) and mark them
  with device_class="NVLinkBridge"; escalate PCIe link speed downgrade to
  Critical for these cards (Gen3 on a fixed internal connector = hardware
  fault, not a transient warning)
- pcie: cross-reference nvidia-smi topo to capture NVLink bond counts and
  active status for all NVLink bridge cards
- packages: add infiniband-diags to ISO; provides ibstat required by
  nvidia-fabricmanager-start.sh to enumerate IB devices before FM launch
  (absence causes CUDA_ERROR_SYSTEM_NOT_READY)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

audit/internal/collector/storage_discovery_test.go

@@ -1,6 +1,7 @@
 package collector
 
 import (
+	"encoding/json"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -38,6 +39,54 @@ func TestParseStorageBytes(t *testing.T) {
 	}
 }
 
+func TestJsonInt64UnmarshalBothFormats(t *testing.T) {
+	t.Parallel()
+
+	// util-linux ≥ 2.37 emits LOG-SEC / PHY-SEC as bare JSON numbers.
+	// Older versions emit quoted strings. Both must parse without error
+	// so that the entire lsblkDevices() call does not return nil on Debian 12.
+	cases := []struct {
+		json string
+		want int64
+	}{
+		{`512`, 512},
+		{`4096`, 4096},
+		{`"512"`, 512},
+		{`"4096"`, 4096},
+		{`null`, 0},
+	}
+	for _, tc := range cases {
+		var v jsonInt64
+		if err := v.UnmarshalJSON([]byte(tc.json)); err != nil {
+			t.Fatalf("UnmarshalJSON(%s): unexpected error %v", tc.json, err)
+		}
+		if int64(v) != tc.want {
+			t.Fatalf("UnmarshalJSON(%s)=%d want %d", tc.json, int64(v), tc.want)
+		}
+	}
+
+	// Simulate the exact JSON shape that triggered the bug on Debian 12.
+	input := []byte(`{
+		"blockdevices": [
+			{"name":"sda","type":"disk","size":"3.6T","serial":"S1234","model":"SEAGATE","tran":"sata","hctl":"0:0:0:0","log-sec":512,"phy-sec":4096},
+			{"name":"sdb","type":"disk","size":"3.6T","serial":"S5678","model":"SEAGATE","tran":"sata","hctl":"0:0:1:0","log-sec":512,"phy-sec":4096}
+		]
+	}`)
+	var root lsblkRoot
+	if err := json.Unmarshal(input, &root); err != nil {
+		t.Fatalf("lsblkRoot unmarshal with integer log-sec/phy-sec: %v", err)
+	}
+	if len(root.Blockdevices) != 2 {
+		t.Fatalf("got %d blockdevices want 2", len(root.Blockdevices))
+	}
+	if int64(root.Blockdevices[0].LogSec) != 512 {
+		t.Fatalf("LogSec=%d want 512", root.Blockdevices[0].LogSec)
+	}
+	if int64(root.Blockdevices[0].PhySec) != 4096 {
+		t.Fatalf("PhySec=%d want 4096", root.Blockdevices[0].PhySec)
+	}
+}
+
 func TestBestEffortRescanHotplugStorage(t *testing.T) {
 	t.Parallel()