sync: bug fixes + eval system from private repo

- Fix chunk_status: pass chunk_status/chunk/metadata to context builder
- Fix vector search: scope by node_id BEFORE similarity search
- Add eval logging system (RAH_EVALS_LOG=1)
- Add eval dashboard at /evals
- Add vitest for testing

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/services/context/requestContext.ts

@@ -12,6 +12,10 @@ interface RequestContext {
     openai?: string;
     anthropic?: string;
   };
+  helperName?: string;
+  evalDatasetId?: string;
+  evalScenarioId?: string;
+  evalChatSpanId?: string;
 }
 
 let currentContext: RequestContext = {};
@@ -26,11 +30,11 @@ export const RequestContext = {
       }
     });
   },
-  
+
   get(): RequestContext {
     return currentContext;
   },
-  
+
   clear() {
     currentContext = {};
   },