[codex] fix empty stream success handling and unknown usage logs (#343)

* fix: preserve repeated short responses deltas

* fix empty stream success handling and unknown usage logs

* fix proxy usage metadata typing

* fix stream bookkeeping and explicit zero usage source

* fix sticky fast path and usage placeholder detection

src/web/pages/helpers/proxyLogPathMeta.ts

@@ -1,10 +1,11 @@
-import { parseProxyLogMetadata } from '../../../shared/proxyLogMeta.js';
+import { parseProxyLogMetadata, type ParsedProxyLogMetadata } from '../../../shared/proxyLogMeta.js';
 
 type ProxyLogPathMeta = {
   clientFamily: string | null;
   sessionId: string | null;
   downstreamPath: string | null;
   upstreamPath: string | null;
+  usageSource: ParsedProxyLogMetadata['usageSource'];
   errorMessage: string;
 };
 
@@ -17,6 +18,7 @@ export function parseProxyLogPathMeta(message?: string): ProxyLogPathMeta {
     sessionId: parsed.sessionId,
     downstreamPath: parsed.downstreamPath,
     upstreamPath: parsed.upstreamPath,
+    usageSource: parsed.usageSource,
     errorMessage: parsed.messageText,
   };
 }