Opening a second vscode window creates a new repo instance

Each vscode window uses its own repo object, which is operating on the same hypermerge data directory. This can very easily cause data corruption.

Repro: Open two vscode windows. Select a document and inspect its feeds in both windows. Make a change in one window. See that the blocks of the locally writable feed increase by one. See that the blocks are unchanged in the other window.

No file or test is named. Start with the two-window reproduction and inspect how each VSCode window creates its repo object over the shared Hypermerge data directory; done means making a change in one window no longer leaves the other operating on conflicting feed state or risking corruption.

Written by the indexing model from the issue text.