fix: use .keyword suffix for text field sorting in OpenSearch

OpenSearch dynamically maps string fields as text with a .keyword
subfield. Sorting on text fields throws an error; only .keyword,
date, and numeric fields support sorting. Add .keyword suffix to
all string sort columns (status, routeId, agentId, executionId,
correlationId, applicationName) while keeping start_time and
duration_ms as-is.

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

cameleer3-server-core/src/main/java/com/cameleer3/server/core/search/SearchRequest.java

@@ -59,16 +59,17 @@ public record SearchRequest(
             "durationMs", "executionId", "applicationName"
     );
 
-    /** Maps camelCase API sort field names to snake_case OpenSearch/DB column names. */
+    /** Maps camelCase API sort field names to OpenSearch field names.
+     *  Text fields use .keyword subfield; date/numeric fields are used directly. */
     private static final java.util.Map<String, String> SORT_FIELD_TO_COLUMN = java.util.Map.ofEntries(
             java.util.Map.entry("startTime", "start_time"),
-            java.util.Map.entry("status", "status"),
-            java.util.Map.entry("agentId", "agent_id"),
-            java.util.Map.entry("routeId", "route_id"),
-            java.util.Map.entry("correlationId", "correlation_id"),
             java.util.Map.entry("durationMs", "duration_ms"),
-            java.util.Map.entry("executionId", "execution_id"),
-            java.util.Map.entry("applicationName", "application_name")
+            java.util.Map.entry("status", "status.keyword"),
+            java.util.Map.entry("agentId", "agent_id.keyword"),
+            java.util.Map.entry("routeId", "route_id.keyword"),
+            java.util.Map.entry("correlationId", "correlation_id.keyword"),
+            java.util.Map.entry("executionId", "execution_id.keyword"),
+            java.util.Map.entry("applicationName", "application_name.keyword")
     );
 
     public SearchRequest {