feat(metrics): single chart engine + full-width stacked layout

- One engine: go-analyze/charts (grafana theme) for all live metrics
- Server chart: CPU temp, CPU load%, mem load%, power W, fan RPMs
- GPU charts: temp, load%, mem%, power W — one card per GPU, added dynamically
- Charts 1400x280px SVG, rendered at width:100% in single-column layout
- Add CPU load (from /proc/stat) and mem load (from /proc/meminfo) to LiveMetricSample
- Add GPU mem utilization to GPUMetricRow (nvidia-smi utilization.memory)
- Document charting architecture in bible-local/architecture/charting.md

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

audit/internal/webui/api.go

@@ -424,7 +424,7 @@ func (h *handler) handleAPIMetricsStream(w http.ResponseWriter, r *http.Request)
 		case <-ticker.C:
 			sample := platform.SampleLiveMetrics()
 
-			// Feed ring buffers for server-side SVG charts
+			// Feed server ring buffers
 			for _, t := range sample.Temps {
 				if t.Name == "CPU" {
 					h.ringCPUTemp.push(t.Celsius)
@@ -432,6 +432,35 @@ func (h *handler) handleAPIMetricsStream(w http.ResponseWriter, r *http.Request)
 				}
 			}
 			h.ringPower.push(sample.PowerW)
+			h.ringCPULoad.push(sample.CPULoadPct)
+			h.ringMemLoad.push(sample.MemLoadPct)
+
+			// Feed fan ring buffers (grow on first sight)
+			h.ringsMu.Lock()
+			for i, fan := range sample.Fans {
+				for len(h.ringFans) <= i {
+					h.ringFans = append(h.ringFans, newMetricsRing(120))
+					h.fanNames = append(h.fanNames, fan.Name)
+				}
+				h.ringFans[i].push(float64(fan.RPM))
+			}
+			// Feed per-GPU ring buffers (grow on first sight)
+			for _, gpu := range sample.GPUs {
+				idx := gpu.GPUIndex
+				for len(h.gpuRings) <= idx {
+					h.gpuRings = append(h.gpuRings, &gpuRings{
+						Temp:    newMetricsRing(120),
+						Util:    newMetricsRing(120),
+						MemUtil: newMetricsRing(120),
+						Power:   newMetricsRing(120),
+					})
+				}
+				h.gpuRings[idx].Temp.push(gpu.TempC)
+				h.gpuRings[idx].Util.push(gpu.UsagePct)
+				h.gpuRings[idx].MemUtil.push(gpu.MemUsagePct)
+				h.gpuRings[idx].Power.push(gpu.PowerW)
+			}
+			h.ringsMu.Unlock()
 
 			b, err := json.Marshal(sample)
 			if err != nil {