More robust extension handling. You can now use pre-release extensions again.

1. Enterprise support!

2. C# and F# now properly render in the chat

3. Qmd support has been restored

4. Experimental @Codebase support in the chat (and coming to the cmd-k soon!)

5. Linter is back!

6. Some fixes to codebase indexing.

Removes a check in the chat that slows the chat down in certain cases.

You can now chat with any codebase. No need to have a Github repo / login through Github.