webui: add "6. Scenario" page — run scriptable test scenarios from removable media through the normal task queue

Exposes the scenario engine (platform.System.RunScenario, added earlier)
in the web UI instead of only the `bee run` CLI: a new nav item lists every
scenarios/*.json found on mounted removable media (GET /api/scenario/list)
and runs one with a click (POST /api/scenario/run), enqueued as a normal
Task with target "scenario" — progress/logs live in Tasks like any other
SAT pack, no separate live-output UI needed.

- app.go: satRunner gains RunScenario, exportManager gains
  ListScenarioFilesOnRemovableMedia/ReadScenarioFromRemovableMedia — both
  already implemented on platform.System, just newly exposed through App.
- webui/tasks.go: taskParams.ScenarioName; runTask's "scenario" case reads
  the file from removable media, parses it, and runs it.
- webui/page_scenario.go: the page itself.

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

audit/internal/webui/api.go

@@ -131,7 +131,7 @@ func defaultTaskPriority(target string, params taskParams) int {
 		return taskPriorityAudit
 	case "nvidia-bench-perf", "nvidia-bench-power", "nvidia-bench-autotune":
 		return taskPriorityBenchmark
-	case "nvidia-stress", "amd-stress", "memory-stress", "sat-stress", "platform-stress", "nvidia-compute":
+	case "nvidia-stress", "amd-stress", "memory-stress", "sat-stress", "platform-stress", "nvidia-compute", "scenario":
 		return taskPriorityBurn
 	case "nvidia", "nvidia-targeted-stress", "nvidia-targeted-power", "nvidia-pulse",
 		"nvidia-interconnect", "nvidia-bandwidth", "memory", "storage", "cpu",
@@ -575,6 +575,61 @@ func (h *handler) handleAPISATRun(target string) http.HandlerFunc {
 	}
 }
 
+// ── Scenario ─────────────────────────────────────────────────────────────────
+
+func (h *handler) handleAPIScenarioList(w http.ResponseWriter, _ *http.Request) {
+	if h.opts.App == nil {
+		writeError(w, http.StatusServiceUnavailable, "app not configured")
+		return
+	}
+	files, err := h.opts.App.ListScenarioFilesOnRemovableMedia()
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+	type scenarioFile struct {
+		Name   string `json:"name"`
+		Device string `json:"device"`
+	}
+	out := make([]scenarioFile, 0, len(files))
+	for _, f := range files {
+		out = append(out, scenarioFile{Name: f.Name, Device: f.Device})
+	}
+	writeJSON(w, out)
+}
+
+func (h *handler) handleAPIScenarioRun(w http.ResponseWriter, r *http.Request) {
+	if h.opts.App == nil {
+		writeError(w, http.StatusServiceUnavailable, "app not configured")
+		return
+	}
+	var body struct {
+		Name string `json:"name"`
+	}
+	if r.Body != nil {
+		if err := json.NewDecoder(r.Body).Decode(&body); err != nil && !errors.Is(err, io.EOF) {
+			writeError(w, http.StatusBadRequest, "invalid request body")
+			return
+		}
+	}
+	name := strings.TrimSpace(body.Name)
+	if name == "" {
+		writeError(w, http.StatusBadRequest, "scenario name is required")
+		return
+	}
+	t := &Task{
+		ID:        newJobID("scenario"),
+		Name:      "Scenario: " + name,
+		Target:    "scenario",
+		Priority:  defaultTaskPriority("scenario", taskParams{}),
+		Status:    TaskPending,
+		CreatedAt: time.Now(),
+	}
+	t.params.ScenarioName = name
+	globalQueue.enqueue(t)
+	writeJSON(w, map[string]string{"task_id": t.ID, "job_id": t.ID})
+}
+
 func (h *handler) handleAPIBenchmarkNvidiaRunKind(target string) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		if h.opts.App == nil {