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/schema.d.ts

@@ -95,6 +95,17 @@ export interface paths {
       };
     };
   };
+  '/search/stats': {
+    get: {
+      responses: {
+        200: {
+          content: {
+            'application/json': ExecutionStats;
+          };
+        };
+      };
+    };
+  };
   '/agents': {
     get: {
       parameters: {
@@ -181,6 +192,11 @@ export interface ProcessorNode {
 /** Processor snapshot is a flat key-value map (Map<String, String> in Java) */
 export type ProcessorSnapshot = Record<string, string>;
 
+export interface ExecutionStats {
+  p99LatencyMs: number;
+  activeCount: number;
+}
+
 export interface AgentInstance {
   agentId: string;
   group: string;