Fixes a performance bug that would happen if you use cmd-k a lot.

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.