fix(sse): make safeLogEvents async — 'await' in a sync function broke every chatHelpers import

#3692 added a lazy 'await import(proxyEgress)' for egress-IP visibility inside
safeLogEvents, which is a sync function — an ES syntax error. It went unnoticed
because typecheck:core does not cover src/sse and no test in the merge gates
loaded chatHelpers via tsx; any consumer that did (chat-context-relay and
chat-route-coverage suites, integration harnesses) failed at module load with
'await can only be used inside an async function'.

safeLogEvents is fire-and-forget logging with an outer try/catch, so making it
async (and 'void'-ing the single chat.ts call site) preserves behavior exactly.

Validation: tests/unit/chat-context-relay.test.ts + chat-route-coverage.test.ts
went from failing-at-load to green (+14 tests destravados).

src/sse/handlers/chat.ts

@@ -1058,8 +1058,8 @@ async function handleSingleModelChat(
         getTargetFormat(provider, credentials.providerSpecificData) ||
         targetFormat;
 
-      // 5. Log proxy + translation events
-      safeLogEvents({
+      // 5. Log proxy + translation events (fire-and-forget; never blocks the response)
+      void safeLogEvents({
         result,
         proxyInfo,
         proxyLatency,

src/sse/handlers/chatHelpers.ts

@@ -592,7 +592,9 @@ export async function safeResolveProxy(connectionId: string, apiKeyId?: string)
   }
 }
 
-export function safeLogEvents({
+// Async because the egress-IP lookup lazy-imports proxyEgress; callers treat
+// this as fire-and-forget logging (the internal try/catch swallows everything).
+export async function safeLogEvents({
   result,
   proxyInfo,
   proxyLatency,