Add HPL (LINPACK) benchmark as validate/stress task

HPL 2.3 from netlib compiled against OpenBLAS with a minimal
single-process MPI stub — no MPI package required in the ISO.
Matrix size is auto-sized to 80% of total RAM at runtime.

Build:
- VERSIONS: HPL_VERSION=2.3, HPL_SHA256=32c5c17d…
- build-hpl.sh: downloads HPL + OpenBLAS from Debian 12 repo,
  compiles xhpl with a self-contained mpi_stub.c
- build.sh: step 80-hpl, injects xhpl + libopenblas into overlay

Runtime:
- bee-hpl: generates HPL.dat (N auto from /proc/meminfo, NB=256,
  P=1 Q=1), runs xhpl, prints standard WR... Gflops output
- platform/hpl.go: RunHPL(), parses WR line → GFlops + PASSED/FAILED
- tasks.go: target "hpl"
- pages.go: LINPACK (HPL) card in validate/stress grid (stress-only)

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

audit/internal/webui/tasks.go

@@ -39,6 +39,7 @@ var taskNames = map[string]string{
 	"nvidia-interconnect":    "NVIDIA Interconnect Test (NCCL all_reduce_perf)",
 	"nvidia-bandwidth":       "NVIDIA Bandwidth Test (NVBandwidth)",
 	"nvidia-stress":          "NVIDIA GPU Stress",
+	"hpl":                    "LINPACK (HPL)",
 	"memory":                 "Memory SAT",
 	"storage":                "Storage SAT",
 	"cpu":                    "CPU SAT",
@@ -739,6 +740,19 @@ func (q *taskQueue) runTask(t *Task, j *jobState, ctx context.Context) {
 			dur = resolveBurnPreset(t.params.BurnProfile).DurationSec
 		}
 		archive, err = runSATStressPackCtx(a, ctx, "", dur, j.append)
+	case "hpl":
+		if a == nil {
+			err = fmt.Errorf("app not configured")
+			break
+		}
+		opts := platform.HPLOptions{
+			MemFraction: 0.80,
+			NB:          256,
+		}
+		archive, err = func() (string, error) {
+			path, _, runErr := a.RunHPL(ctx, "", opts, j.append)
+			return path, runErr
+		}()
 	case "platform-stress":
 		if a == nil {
 			err = fmt.Errorf("app not configured")