fix(gateway): guard indexed message access for noUncheckedIndexedAccess

`body.messages[i]` is `| undefined` under the package's strict tsconfig —
broke the Docker image build (tsc) after the latest-user-message block fix.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: patel-lyzr

packages/llm-proxy-openai/src/proxy.ts

@@ -327,7 +327,7 @@ async function redactAnthropicRequest(
   // Index of the most recent user message — the only span allowed to block.
   let lastUserIdx = -1;
   for (let i = body.messages.length - 1; i >= 0; i--) {
-    if (body.messages[i].role === "user") { lastUserIdx = i; break; }
+    if (body.messages[i]?.role === "user") { lastUserIdx = i; break; }
   }
 
   // system prompt — redact only, never block
@@ -344,6 +344,7 @@ async function redactAnthropicRequest(
   // messages — redact all; honour `block` only for the latest user message
   for (let i = 0; i < body.messages.length; i++) {
     const msg = body.messages[i];
+    if (!msg) continue;
     const canBlock = i === lastUserIdx;
     if (typeof msg.content === "string") {
       const r = await redact(msg.content);