fix: send file-done before closing file DC to avoid control channel race

Closing the file DataChannel can trigger SCTP/ICE cleanup before the
file-done control message is flushed, causing a 15 s timeout on the
receiver. Send file-done first on both the Go and TS sender paths.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

cli/internal/transport/transport.go

@@ -758,11 +758,12 @@ func (s *Session) SendFile(path string) error {
 			return err
 		}
 	}
+	// §9: send file-done before closing the file DC so the control channel
+	// is still reachable when the message is delivered.
+	s.controlSend(map[string]string{"type": "file-done", "xid": xid, "sha256": sha256hex})
 	if err := dc.Close(); err != nil {
 		return err
 	}
-	// §9: send file-done with the pre-computed hash so the receiver can verify.
-	s.controlSend(map[string]string{"type": "file-done", "xid": xid, "sha256": sha256hex})
 	return nil
 }
 

pwa/src/transport/flit.ts

@@ -510,9 +510,10 @@ export class PeerConn {
       this.events.fileSendProgress?.({ peer: this.peerId, xid, name: file.name, sent: resumeOffset + localOffset, total: file.size })
       await new Promise(r => setTimeout(r, 0))
     }
-    dc.close()
-    // §9: send file-done with sha256 so receiver can verify integrity.
+    // §9: send file-done before closing the file DC so the control channel
+    // is still healthy when the message is dispatched.
     this._dc({ type: 'file-done', xid, sha256: hash })
+    dc.close()
     this.events.fileSent?.({ peer: this.peerId, xid, name: file.name })
   }