Contract-first API with DTOs, validation, and server-side OpenAPI post-processing

Add dedicated request/response DTOs for all controllers, replacing raw
JsonNode parameters with validated types. Move OpenAPI path-prefix stripping
and ProcessorNode children injection into OpenApiCustomizer beans so the
spec served at /api/v1/api-docs is already clean — eliminating the need for
the ui/scripts/process-openapi.mjs post-processing script.

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

ui/src/api/queries/executions.ts

@@ -1,12 +1,6 @@
 import { useQuery } from '@tanstack/react-query';
 import { api } from '../client';
-import type {
-  SearchRequest,
-  ExecutionStats,
-  ExecutionSummary,
-  StatsTimeseries,
-  ExecutionDetail,
-} from '../schema-types';
+import type { SearchRequest } from '../types';
 
 export function useExecutionStats(timeFrom: string | undefined, timeTo: string | undefined) {
   return useQuery({
@@ -21,7 +15,7 @@ export function useExecutionStats(timeFrom: string | undefined, timeTo: string |
         },
       });
       if (error) throw new Error('Failed to load stats');
-      return data as unknown as ExecutionStats;
+      return data!;
     },
     enabled: !!timeFrom,
     placeholderData: (prev) => prev,
@@ -37,7 +31,7 @@ export function useSearchExecutions(filters: SearchRequest, live = false) {
         body: filters,
       });
       if (error) throw new Error('Search failed');
-      return data as unknown as { data: ExecutionSummary[]; total: number; offset: number; limit: number };
+      return data!;
     },
     placeholderData: (prev) => prev,
     refetchInterval: live ? 5_000 : false,
@@ -58,7 +52,7 @@ export function useStatsTimeseries(timeFrom: string | undefined, timeTo: string
         },
       });
       if (error) throw new Error('Failed to load timeseries');
-      return data as unknown as StatsTimeseries;
+      return data!;
     },
     enabled: !!timeFrom,
     placeholderData: (prev) => prev,
@@ -74,7 +68,7 @@ export function useExecutionDetail(executionId: string | null) {
         params: { path: { executionId: executionId! } },
       });
       if (error) throw new Error('Failed to load execution detail');
-      return data as unknown as ExecutionDetail;
+      return data!;
     },
     enabled: !!executionId,
   });
@@ -96,7 +90,7 @@ export function useProcessorSnapshot(
         },
       );
       if (error) throw new Error('Failed to load snapshot');
-      return data as unknown as Record<string, string>;
+      return data!;
     },
     enabled: !!executionId && index !== null,
   });