Restructure web UI navigation into 7 numbered workflow stages

Replace the flat menu (Dashboard, Audit, Validate, Burn, Benchmark,
Tasks, Tools) with a numbered progression that guides engineers through
a logical acceptance workflow:

  Dashboard (landing) → 1. Audit → 2. Check → 3. Load → 4. Speed
  → 5. Endurance → 6. Tools → 7. Settings

Key changes:
- layout.go: numbered nav labels, new hrefs, Tasks removed from nav
  and replaced with a persistent sidebar badge (polls /api/tasks every
  5 s, highlights amber when tasks are active)
- server.go: 301 redirects from /validate→/check, /burn→/load,
  /benchmark→/speed for backward compatibility
- pages.go: dispatch cases for all new routes; old routes kept as
  fallbacks
- page_validate.go: add renderCheck() — non-destructive check page
  with validate-mode tests only (no stress toggle, no targeted-stress/
  targeted-power/pulse cards)
- page_burn.go: add renderLoad() wrapper; update scope alert to
  reference /check instead of /validate
- page_benchmark.go: add renderSpeed() (performance focus) and
  renderEndurance() (stability/overnight focus) wrappers
- page_settings.go: new Settings page with blackbox logging toggle,
  NVIDIA driver reset, and build info
- server_test.go: update five tests to use new route names and
  content expectations

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

audit/internal/webui/page_benchmark.go

@@ -611,3 +611,20 @@ func renderPowerBenchmarkResultsCard(exportDir string) string {
 	b.WriteString(`</div></div>`)
 	return b.String()
 }
+
+// renderSpeed renders the Speed page (step 4): performance benchmarks.
+// Uses the same benchmark infrastructure; defaults to Standard profile (throughput/bandwidth).
+// For long-duration stability/overnight runs, see Endurance (step 5).
+func renderSpeed(opts HandlerOptions) string {
+	base := renderBenchmark(opts)
+	return `<div class="alert alert-info" style="margin-bottom:16px"><strong>Speed:</strong> Measures GPU compute throughput and memory bandwidth. For overnight stability testing, go to <a href="/endurance">5. Endurance</a>.</div>` + base
+}
+
+// renderEndurance renders the Endurance page (step 5): long-duration reliability tests.
+// Focuses on Stability and Overnight profiles for multi-hour burn validation.
+// For short load tests, see Load (step 3). For throughput measurement, see Speed (step 4).
+func renderEndurance(opts HandlerOptions) string {
+	base := renderBenchmark(opts)
+	return `<div class="alert alert-warn" style="margin-bottom:16px"><strong>Endurance:</strong> Long-duration reliability tests — Stability (several hours) and Overnight (8+ h) profiles. These profiles run hardware at sustained load; results show whether the server holds its performance envelope over time.</div>
+<div class="alert alert-info" style="margin-bottom:16px">Use the <strong>Stability</strong> or <strong>Overnight</strong> profile in the setup card below. The Standard profile is available too but is better suited for the <a href="/speed">4. Speed</a> page.</div>` + base
+}