Add scripting dictionary commands for activating windows, selecting tabs,
closing tabs, and closing windows.
Implement the corresponding Cocoa AppleScript command handlers and expose
minimal ScriptWindow/ScriptTab helpers needed to resolve live targets.
Verified by building Ghostty and running osascript commands against the
absolute Debug app path to exercise all four new commands.
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.