Remove Factory visualization code

[williamthorsen]

Parent: #173

Goal

Delete the retired Factory visualization once the catwalk is validated (after milestone 1).

Tasks

• Remove src/client/game/ directory (scenes, actors, layout, mappers, state, sprites)
• Remove GameCanvas.tsx
• Remove 'factory' from the visualization switcher (or repurpose it as an alias for 'catwalk')
• Remove any Factory-specific test files
• Clean up unused imports and dead code

Prerequisite

Catwalk milestone 1 must be complete and validated.