feat: add container-use package and fix goose-cli libclang dependency

- Add dagger/container-use (v0.4.2) for containerized coding agent environments
- Fix goose-cli build by adding llvmPackages.libclang for bindgen
- Clean up skillsmcp package (remove custom fastmcp override, use nixos-unstable)
- Remove broken update.py script from goose-cli
- Add treefmt.toml for consistent formatting
- Update README with all current packages

packages/skillsmcp/default.nix

@@ -1,4 +1 @@
-{ pkgs, ... }:
-pkgs.callPackage ./package.nix {
-  fastmcp = pkgs.callPackage ./fastmcp.nix { };
-}
+{ pkgs, ... }: pkgs.callPackage ./package.nix { }