Add two new AppleScript commands to the scripting dictionary:
- `focus terminal <terminal>` — focuses the given terminal and brings
its window to the front.
- `close terminal <terminal>` — closes the given terminal without a
confirmation prompt.
Each command is implemented as an NSScriptCommand subclass following
the same pattern as the existing split command.
This is an update to address common agentic issues I run into,
but the `build.nu` script may be generally helpful to people using
the Nix env since `xcodebuild` is broken by default in Nix due to the
compiler/linker overrides Nix shell does.
