Fix UI types to match actual backend API

Validated against live OpenAPI spec at /api/v1/api-docs. Fixes:
- duration → durationMs (all models)
- Remove processorCount (not in ExecutionSummary)
- Remove ProcessorNode.index and .uri (not in backend)
- ProcessorSnapshot is Record<string,string>, not structured object
- Add missing fields: endTime, diagramContentHash, exchangeId, etc.
- Save openapi.json from live server

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

ui/src/pages/executions/ExecutionExplorer.tsx

@@ -17,7 +17,7 @@ export function ExecutionExplorer() {
   // Derive stats from current search results
   const failedCount = results.filter((r) => r.status === 'FAILED').length;
   const avgDuration = results.length > 0
-    ? Math.round(results.reduce((sum, r) => sum + r.duration, 0) / results.length)
+    ? Math.round(results.reduce((sum, r) => sum + r.durationMs, 0) / results.length)
     : 0;
 
   const showFrom = total > 0 ? offset + 1 : 0;