Fix GPU clock lock normalization for Blackwell (clocks.max.* unsupported)

clocks.max.graphics / clocks.max.memory CSV fields return exit status 2 on
RTX PRO 6000 Blackwell (driver 98.x), causing the entire gpu inventory query
to fail and clock lock to be skipped → normalization: partial.

Fix:
- Add minimal fallback query (index,uuid,name,pci.bus_id,vbios_version,
  power.limit) that succeeds even without clock fields
- Add enrichGPUInfoWithMaxClocks: parses "Max Clocks" section of
  nvidia-smi -q verbose output to fill MaxGraphicsClockMHz /
  MaxMemoryClockMHz when CSV fields fail
- Move nvidia-smi -q execution before queryBenchmarkGPUInfo so its output
  is available for clock enrichment immediately after
- Tests: cover enrichment and skip-if-populated cases

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

audit/internal/platform/benchmark_test.go

@@ -178,3 +178,67 @@ func TestRenderBenchmarkReportIncludesTerminalChartsWithoutANSI(t *testing.T) {
 		t.Fatalf("report should not contain ANSI escapes\n%s", report)
 	}
 }
+
+func TestEnrichGPUInfoWithMaxClocks(t *testing.T) {
+	t.Parallel()
+
+	nvsmiQ := []byte(`
+GPU 00000000:4E:00.0
+    Product Name                          : NVIDIA RTX PRO 6000 Blackwell Server Edition
+    Clocks
+        Graphics                          : 2422 MHz
+        Memory                            : 12481 MHz
+    Max Clocks
+        Graphics                          : 2430 MHz
+        SM                                : 2430 MHz
+        Memory                            : 12481 MHz
+        Video                             : 2107 MHz
+
+GPU 00000000:4F:00.0
+    Product Name                          : NVIDIA RTX PRO 6000 Blackwell Server Edition
+    Max Clocks
+        Graphics                          : 2430 MHz
+        Memory                            : 12481 MHz
+`)
+
+	infoByIndex := map[int]benchmarkGPUInfo{
+		0: {Index: 0, BusID: "00000000:4E:00.0"},
+		1: {Index: 1, BusID: "00000000:4F:00.0"},
+	}
+
+	enrichGPUInfoWithMaxClocks(infoByIndex, nvsmiQ)
+
+	if infoByIndex[0].MaxGraphicsClockMHz != 2430 {
+		t.Errorf("GPU 0 MaxGraphicsClockMHz = %v, want 2430", infoByIndex[0].MaxGraphicsClockMHz)
+	}
+	if infoByIndex[0].MaxMemoryClockMHz != 12481 {
+		t.Errorf("GPU 0 MaxMemoryClockMHz = %v, want 12481", infoByIndex[0].MaxMemoryClockMHz)
+	}
+	if infoByIndex[1].MaxGraphicsClockMHz != 2430 {
+		t.Errorf("GPU 1 MaxGraphicsClockMHz = %v, want 2430", infoByIndex[1].MaxGraphicsClockMHz)
+	}
+	if infoByIndex[1].MaxMemoryClockMHz != 12481 {
+		t.Errorf("GPU 1 MaxMemoryClockMHz = %v, want 12481", infoByIndex[1].MaxMemoryClockMHz)
+	}
+}
+
+func TestEnrichGPUInfoWithMaxClocksSkipsPopulated(t *testing.T) {
+	t.Parallel()
+
+	nvsmiQ := []byte(`
+GPU 00000000:4E:00.0
+    Max Clocks
+        Graphics                          : 9999 MHz
+        Memory                            : 9999 MHz
+`)
+	// Already populated — must not be overwritten.
+	infoByIndex := map[int]benchmarkGPUInfo{
+		0: {Index: 0, BusID: "00000000:4E:00.0", MaxGraphicsClockMHz: 2430, MaxMemoryClockMHz: 12481},
+	}
+
+	enrichGPUInfoWithMaxClocks(infoByIndex, nvsmiQ)
+
+	if infoByIndex[0].MaxGraphicsClockMHz != 2430 {
+		t.Errorf("expected existing value to be preserved, got %v", infoByIndex[0].MaxGraphicsClockMHz)
+	}
+}