Add vLLM v0.18.1 source tree with KV transfer abort fix

third_party/vllm/ now tracked in git for direct patch management.
Based on vLLM v0.18.1 release with one patch applied:

  vllm/v1/core/sched/scheduler.py:
    Replace fatal assert with graceful skip when KV transfer callback
    arrives for an already-aborted request during PD disaggregated serving.

Future vLLM modifications should be made directly in third_party/vllm/
and committed normally. The patches/ directory is kept as documentation
of what changed from upstream.

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

third_party/vllm/examples/online_serving/dashboards/README.md

@@ -0,0 +1,87 @@
+# Monitoring Dashboards
+
+This directory contains monitoring dashboard configurations for vLLM, providing
+comprehensive observability for your vLLM deployments.
+
+## Dashboard Platforms
+
+We provide dashboards for two popular observability platforms:
+
+- **[Grafana](https://grafana.com)**
+- **[Perses](https://perses.dev)**
+
+## Dashboard Format Approach
+
+All dashboards are provided in **native formats** that work across different
+deployment methods:
+
+### Grafana (JSON)
+
+- ✅ Works with any Grafana instance (cloud, self-hosted, Docker)
+- ✅ Direct import via Grafana UI or API
+- ✅ Can be wrapped in Kubernetes operators when needed
+- ✅ No vendor lock-in or deployment dependencies
+
+### Perses (YAML)
+
+- ✅ Works with standalone Perses instances
+- ✅ Compatible with Perses API and CLI
+- ✅ Supports Dashboard-as-Code workflows
+- ✅ Can be wrapped in Kubernetes operators when needed
+
+## Dashboard Contents
+
+Both platforms provide equivalent monitoring capabilities:
+
+| Dashboard | Description |
+| --------- | ----------- |
+| **Performance Statistics** | Tracks latency, throughput, and performance metrics |
+| **Query Statistics** | Monitors request volume, query performance, and KPIs |
+
+## Quick Start
+
+First, navigate to this example's directory:
+
+```bash
+cd examples/online_serving/dashboards
+```
+
+### Grafana
+
+Import the JSON directly into the Grafana UI, or use the API:
+
+```bash
+curl -X POST http://grafana/api/dashboards/db \
+  -H "Content-Type: application/json" \
+  -d @grafana/performance_statistics.json
+```
+
+### Perses
+
+Import via the Perses CLI:
+
+```bash
+percli apply -f perses/performance_statistics.yaml
+```
+
+## Requirements
+
+- **Prometheus** metrics from your vLLM deployment
+- **Data source** configured in your monitoring platform
+- **vLLM metrics** enabled and accessible
+
+## Platform-Specific Documentation
+
+For detailed deployment instructions and platform-specific options, see:
+
+- **[Grafana Documentation](./grafana)** - JSON dashboards, operator usage, manual import
+- **[Perses Documentation](./perses)** - YAML specs, CLI usage, operator wrapping
+
+## Contributing
+
+When adding new dashboards, please:
+
+1. Provide native formats (JSON for Grafana, YAML specs for Perses)
+2. Update platform-specific README files
+3. Ensure dashboards work across deployment methods
+4. Test with the latest platform versions