Add harness app: agent orchestrator with cluster deployment

- Next.js app for orchestrating coding agent benchmarks (Claude Code, Codex, OpenCode)
- Dockerfile installs git, gh CLI, and agent CLIs for headless execution
- K8s deployment with workspace volume, sealed credentials for Claude + OpenCode
- Traefik IngressRoute at harness.coreworlds.io with internal-only middleware + TLS
- CI pipeline path filter for harness builds
- Fix OpenCode runtime flags (subcommand-based headless mode)

.github/workflows/ci.yaml

@@ -27,6 +27,9 @@ jobs:
             api:
               - 'apps/api/**'
               - 'packages/**'
+            harness:
+              - 'apps/harness/**'
+              - 'packages/**'
 
   lint-and-test:
     runs-on: ubuntu-latest