The `ComputerUseProviderTool` function needed a little bit of an
adjustment because I changed `NewComputerUseTool`'s signature in
upstream fantasy a little bit.
- Moves `coderd/chatd/`, `coderd/gitsync/`, `enterprise/coderd/chatd/`
under `x/` parent directories to signal instability
- Adds `Experimental:` glue code comments in `coderd/coderd.go`
> 🤖 This PR was created with the help of Coder Agents, and was
reviewed by my human. 🧑💻