Promote subsystem namespaces to the top level of the module

System, Display, Graphics, Sprite, Sound, File, JSON, Lua, Scoreboards,
Network, Rect, SystemEvent, and AccessReply now live at module scope
instead of being nested in the Playdate enum; consumers write
System.log(...) instead of Playdate.System.log(...), and can qualify with
the module name (PlayDate.System) on collision. The Playdate enum remains
only as the raw C API bootstrap (initialize(with:), api, apiPointer), and
Playdate.Error is renamed PlaydateError so no top-level type shadows
Swift.Error.

Breaking change for any existing consumers.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Sources/PlayDate/Graphics.swift

@@ -7,14 +7,12 @@
 
 internal import CPlaydate
 
-extension Playdate {
-    /// The graphics API: drawing, bitmaps, fonts, tilemaps, and video.
-    public enum Graphics {}
-}
+/// The graphics API: drawing, bitmaps, fonts, tilemaps, and video.
+public enum Graphics {}
 
 var gfx: playdate_graphics { Playdate.api.graphics.pointee }
 
-extension Playdate.Graphics {
+extension Graphics {
     // MARK: - Screen constants
 
     /// The width of the screen in pixels (`LCD_COLUMNS`).