All four SMBC modes now dispatch

The GameMode skeleton is in, part of issue #10 — with it, OperModeExecutionTree dispatches all four modes. What's translatable without the player, enemy and area-parser atoms now runs: the task tree with SecondaryGameSetup wired in, GameCoreRoutine's master joypad copy (the current player's controller bits become the game's single set) and its task gate, and the GameEngine's tail — the star-music check that re-attains the level theme when the invincibility timer hits exactly 4 with the interval timer expired, the palette-cycle control computation, SaveAB and UpdScrollVar.

What waits

The thirteen GameRoutines entries (player entrance, death, flagpole, fire flower and friends), InitializeArea, ScreenRoutines, and the engine's object-processing calls are stubbed in place with TODO(port) markers naming their atoms. That's the bulk of the game — the player atom alone holds physics, collision and graphics — and it lands piece by piece from here.

Tests cover the joypad master copy, the setup task not running the core early, the SaveAB tail, both star-music gates and the scroll wrap. make test is green.