feat: add interactive ProcessDiagram SVG component (sub-project 1/3)

New interactive route diagram component with SVG rendering using
server-computed ELK layout coordinates. TIBCO BW5-inspired top-bar
card node style with zoom/pan, hover toolbars, config badges, and
error handler sections below the main flow.

Backend: add direction query parameter (LR/TB) to diagram render
endpoints, defaulting to left-to-right layout.

Frontend: 14-file ProcessDiagram component in ui/src/components/
with DiagramNode, CompoundNode, DiagramEdge, ConfigBadge, NodeToolbar,
ErrorSection, ZoomControls, and supporting hooks. Dev test page at
/dev/diagram for validation.

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

cameleer3-server-app/src/main/java/com/cameleer3/server/app/controller/DiagramRenderController.java

@@ -62,6 +62,7 @@ public class DiagramRenderController {
     @ApiResponse(responseCode = "404", description = "Diagram not found")
     public ResponseEntity<?> renderDiagram(
             @PathVariable String contentHash,
+            @RequestParam(defaultValue = "LR") String direction,
             HttpServletRequest request) {
 
         Optional<RouteGraph> graphOpt = diagramStore.findByContentHash(contentHash);
@@ -76,7 +77,7 @@ public class DiagramRenderController {
         // without also accepting everything (*/*). This means "application/json"
         // must appear and wildcards must not dominate the preference.
         if (accept != null && isJsonPreferred(accept)) {
-            DiagramLayout layout = diagramRenderer.layoutJson(graph);
+            DiagramLayout layout = diagramRenderer.layoutJson(graph, direction);
             return ResponseEntity.ok()
                     .contentType(MediaType.APPLICATION_JSON)
                     .body(layout);
@@ -96,7 +97,8 @@ public class DiagramRenderController {
     @ApiResponse(responseCode = "404", description = "No diagram found for the given application and route")
     public ResponseEntity<DiagramLayout> findByApplicationAndRoute(
             @RequestParam String application,
-            @RequestParam String routeId) {
+            @RequestParam String routeId,
+            @RequestParam(defaultValue = "LR") String direction) {
         List<String> agentIds = registryService.findByApplication(application).stream()
                 .map(AgentInfo::id)
                 .toList();
@@ -115,7 +117,7 @@ public class DiagramRenderController {
             return ResponseEntity.notFound().build();
         }
 
-        DiagramLayout layout = diagramRenderer.layoutJson(graphOpt.get());
+        DiagramLayout layout = diagramRenderer.layoutJson(graphOpt.get(), direction);
         return ResponseEntity.ok(layout);
     }