Fix Codex transcript streaming and images

server/src/session/transport.rs

@@ -252,6 +252,12 @@ impl Transport {
     /// would otherwise need a runtime to ask a machine a question. Both build the
     /// invocation the same way.
     pub fn capture_blocking(&self, launch: &Launch) -> Result<String> {
+        Ok(String::from_utf8_lossy(&self.capture_bytes_blocking(launch)?).into_owned())
+    }
+
+    /// The byte-preserving form of [`capture_blocking`](Self::capture_blocking), used when a
+    /// driver copies a file back from the machine it runs on.
+    pub fn capture_bytes_blocking(&self, launch: &Launch) -> Result<Vec<u8>> {
         let host = match self {
             Self::Here => None,
             Self::Ssh { ssh, .. } => Some(ssh),
@@ -273,7 +279,7 @@ impl Transport {
                 stderr
             });
         }
-        Ok(String::from_utf8_lossy(&output.stdout).into_owned())
+        Ok(output.stdout)
     }
 
     /// Runs `launch` with `input` on its stdin and reports everything it