Streamline App Store screenshot capture

[austin-smith]

What Changed

• Add runtime controls for platform targets, game selection, device coverage, card style, dark mode, and build reuse.
• Make the fast default capture the top three games on the required iPhone and iPad sizes.
• Split screenshot fixtures into individually selectable UI tests.
• Preserve platform-native card defaults while allowing explicit Classic, Simple, or Pixel captures.
• Keep macOS capture opt-in and forward appearance settings through the XCTest runner environment.

Why

The previous lane always generated every game on every platform and rebuilt more than necessary. This makes focused App Store screenshot runs substantially faster while retaining full-set and macOS options when needed.

Validation

• Generated and visually inspected dark-mode Simple and Pixel screenshots for Klondike, Spider, and FreeCell on 11-inch and 13-inch iPads.
• Passed iOS Simulator and macOS screenshot-target build-for-testing validation.
• Passed Fastfile Ruby syntax validation and git diff --check.
• Completed a clean structured pre-ship review.