Fix status filter OR logic and add P99/active stats endpoint

Status filter now parses comma-separated values into SQL IN clause
instead of exact match, so filtering by multiple statuses works.

Added GET /api/v1/search/stats returning P99 latency (last hour) and
active execution count, wired into the UI stat cards with 10s polling.

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

ui/src/api/queries/executions.ts

@@ -2,6 +2,18 @@ import { useQuery } from '@tanstack/react-query';
 import { api } from '../client';
 import type { SearchRequest } from '../schema';
 
+export function useExecutionStats() {
+  return useQuery({
+    queryKey: ['executions', 'stats'],
+    queryFn: async () => {
+      const { data, error } = await api.GET('/search/stats');
+      if (error) throw new Error('Failed to load stats');
+      return data!;
+    },
+    refetchInterval: 10_000,
+  });
+}
+
 export function useSearchExecutions(filters: SearchRequest) {
   return useQuery({
     queryKey: ['executions', 'search', filters],