Collaborative document editor fixes
Documents opened to a permanent loading skeleton and never showed their contents. The live-collaboration handshake now completes correctly.
Two faults were stopping collaborative documents from loading.
- The editor connected to the server and reported itself online, but the opening sync message was discarded before it arrived. Because the server only replies once it receives that message, the document never finished loading and sat on its placeholder skeleton indefinitely.
- A second fault meant no data was relayed between the browser and the server at all, even though the session appeared to open.
Both are resolved — documents now load their contents and live editing works as intended.