fix: wrap streaming reader in try/finally to release lock and prevent resource leaks

Partially addresses #112. The streaming reader in openaiStreamToAnthropic
had no error handling - if an error occurred during streaming, the reader
lock was never released. Wrapped the while loop in try/finally to ensure
reader.releaseLock() is always called.

src/services/api/openaiShim.ts

@@ -412,6 +412,7 @@ async function* openaiStreamToAnthropic(
   const decoder = new TextDecoder()
   let buffer = ''
 
+  try {
     while (true) {
       const { done, value } = await reader.read()
       if (done) break
@@ -567,6 +568,9 @@ async function* openaiStreamToAnthropic(
       }
     }
     }
+  } finally {
+    reader.releaseLock()
+  }
 
   yield { type: 'message_stop' }
 }