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>

app/api/evals/comment/route.ts

@@ -0,0 +1,24 @@
+import { NextRequest } from 'next/server';
+import { upsertEvalComment } from '@/services/evals/evalsStore';
+
+export async function POST(request: NextRequest) {
+  const evalsEnabled = process.env.RAH_EVALS_LOG === '1' || process.env.RAH_EVALS_LOG === 'true';
+  if (process.env.NODE_ENV === 'production' || !evalsEnabled) {
+    return new Response('Not Found', { status: 404 });
+  }
+
+  const body = await request.json();
+  const traceId = typeof body?.traceId === 'string' ? body.traceId : null;
+  const scenarioId = typeof body?.scenarioId === 'string' ? body.scenarioId : null;
+  const comment = typeof body?.comment === 'string' ? body.comment : null;
+
+  if (!traceId || comment === null) {
+    return new Response(JSON.stringify({ error: 'Invalid payload' }), { status: 400 });
+  }
+
+  upsertEvalComment(traceId, scenarioId, comment);
+  return new Response(JSON.stringify({ ok: true }), {
+    status: 200,
+    headers: { 'Content-Type': 'application/json' },
+  });
+}