fix(spa): a reconnect no longer fails the download it reconnects for

While a reconnect ran, every request went out, not only its handshake: a
chunk retried between the new channel opening and the proof got
"Handshake required", which no retry treats as a dropped connection.
Only the opening messages pass now; a replaced channel's late close
event is ignored, and a closed channel is retried like a lost one.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/packages/meshbay-hub/src/meshbay_hub/static/file-utils.js b/packages/meshbay-hub/src/meshbay_hub/static/file-utils.js
index 585558f..ae6cd6f 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/file-utils.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/file-utils.js
@@ -349,9 +349,13 @@ async function _writeOrStall(writable, bytes, at) {
   }
 }
 
+// "Transport closed" is not here: that is close(), somebody ending the
+// connection on purpose. "DataChannel closed" is the channel going away under
+// it, which is what a reconnect is for.
 function _isRetryableTransportError(err) {
   return err.name === 'TransportLostError'
     || err.message === 'Response timeout'
+    || err.message === 'DataChannel closed'
     || (err.message || '').startsWith('DataChannel not open');
 }