feat(docs): add Nexus Shield guardrail integration guide

docs.json

@@ -524,6 +524,7 @@
                   "integrations/guardrails/lasso",
                   "integrations/guardrails/lakera",
                   "integrations/guardrails/mistral",
+                  "integrations/guardrails/nexus-shield",
                   "integrations/guardrails/pangea",
                   "integrations/guardrails/patronus-ai",
                   "integrations/guardrails/palo-alto-panw-prisma",

integrations/guardrails/nexus-shield.mdx

@@ -0,0 +1,44 @@
+---
+title: "Nexus Shield"
+description: "Sub-10ms in-RAM PII sanitization and security guardrail proxy for Portkey"
+---
+
+# Nexus Shield (Sub-10ms Guardrail Proxy)
+
+Nexus Shield is an in-RAM PII sanitization and security guardrail proxy designed for LLM APIs with sub-10ms overhead.
+
+## Usage with Portkey
+
+You can route requests through Nexus Shield by passing its proxy endpoint in your Portkey configuration via `baseURL` or custom headers.
+
+```python
+from portkey_ai import Portkey
+
+portkey = Portkey(
+    api_key="PORTKEY_API_KEY",
+    base_url="https://api.nexusshield.ai/v1",
+    custom_headers={"x-nexus-api-key": "nx_live_YOUR_KEY"},
+)
+
+response = portkey.chat.completions.create(
+    model="gpt-4o",
+    messages=[{"role": "user", "content": "Hello, my phone is 555-0199"}],
+)
+
+print(response)
+```
+
+## Key Features
+
+- **Sub-10ms Latency:** Pattern matching evaluated directly in RAM.
+- **Zero-Log Infrastructure:** Redacts PII without writing raw payloads to disk.
+
+## Get a Trial API Key
+
+Start a 14-day free trial at [api.nexusshield.ai](https://api.nexusshield.ai) or call:
+
+```bash
+curl -X POST https://api.nexusshield.ai/v1/auth/register-trial \
+  -H "Content-Type: application/json" \
+  -d '{"email":"you@company.com"}'
+```