feat: use endpointUri for cross-route drill-down instead of label parsing

Server:
- Add endpointUri to PositionedNode (from RouteNode)
- Add fromEndpointUri to RouteSummary (catalog API)
- Catalog controller resolves endpoint URI from diagram store

UI:
- Build endpointRouteMap from catalog's fromEndpointUri field
- Drill-down uses exact match on node.endpointUri against the map
- Remove label parsing heuristics (extractTargetEndpoint, camelToKebab)

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

ui/src/components/ExecutionDiagram/ExecutionDiagram.tsx

@@ -14,6 +14,7 @@ interface ExecutionDiagramProps {
   executionDetail?: ExecutionDetail;
   direction?: 'LR' | 'TB';
   knownRouteIds?: Set<string>;
+  endpointRouteMap?: Map<string, string>;
   onNodeAction?: (nodeId: string, action: NodeAction) => void;
   nodeConfigs?: Map<string, NodeConfig>;
   className?: string;
@@ -58,6 +59,7 @@ export function ExecutionDiagram({
   executionDetail: externalDetail,
   direction = 'LR',
   knownRouteIds,
+  endpointRouteMap,
   onNodeAction,
   nodeConfigs,
   className,
@@ -166,6 +168,7 @@ export function ExecutionDiagram({
           onNodeAction={onNodeAction}
           nodeConfigs={nodeConfigs}
           knownRouteIds={knownRouteIds}
+          endpointRouteMap={endpointRouteMap}
           executionOverlay={overlay}
           iterationState={iterationState}
           onIterationChange={setIteration}