feat: combine process diagram and processor table into toggled card

Dashboard L3 now shows a single Processor Metrics card with
Diagram/Table toggle buttons. The diagram shows native tooltips on
hover with full processor metrics (avg, p99, invocations, error rate,
% time).

Also fixes:
- Chart x-axis uses actual timestamps instead of bucket indices
- formatDurationShort uses locale formatting with max 3 decimals

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/components/ProcessDiagram/DiagramNode.tsx

@@ -102,6 +102,18 @@ export function DiagramNode({
       style={{ cursor: 'pointer' }}
       opacity={isSkipped ? 0.35 : undefined}
     >
+      {/* Processor metrics tooltip */}
+      {heatmapEntry && (
+        <title>{[
+          `${node.id}${heatmapEntry.processorType ? ` (${heatmapEntry.processorType})` : ''}`,
+          `Avg: ${heatmapEntry.avgDurationMs.toLocaleString(undefined, { maximumFractionDigits: 3 })}ms`,
+          `P99: ${heatmapEntry.p99DurationMs.toLocaleString(undefined, { maximumFractionDigits: 3 })}ms`,
+          `Time: ${heatmapEntry.pctOfRoute.toFixed(1)}%`,
+          heatmapEntry.totalCount != null ? `Invocations: ${heatmapEntry.totalCount.toLocaleString()}` : '',
+          heatmapEntry.errorRate != null ? `Errors: ${(heatmapEntry.errorRate * 100).toFixed(2)}%` : '',
+        ].filter(Boolean).join('\n')}</title>
+      )}
+
       {/* Selection ring */}
       {isSelected && (
         <rect

ui/src/components/ProcessDiagram/types.ts

@@ -21,6 +21,10 @@ export interface LatencyHeatmapEntry {
   p99DurationMs: number;
   /** Percentage of total route time this processor consumes (0-100) */
   pctOfRoute: number;
+  /** Additional fields for diagram tooltip (optional — populated by dashboard) */
+  processorType?: string;
+  totalCount?: number;
+  errorRate?: number;
 }
 
 export interface ProcessDiagramProps {