refactor: modularize architecture with test coverage

[ShadowoftheRavens]

Description

This PR refactors the 7th Sea Dice Roller application from a monolithic structure into a modular, layered architecture with comprehensive test coverage.

Changes

Architecture Refactoring

• Modularization: Split app.mjs into 5 focused modules:

  • controller.mjs - Event binding and action dispatch
  • renderer.mjs - DOM rendering and markup generation
  • app-state.mjs - State shape and mutations
  • dice-service.mjs - Dice rolling and explosion mechanics
  • app-logic.mjs - Partition search algorithm and game logic

• Styling: Extracted all CSS into styles.css for separation of concerns

• Constants: Created constants.mjs with centralized:

  • Scoring weights (increment: 1M, leftover: 1K)
  • Game configuration (targets 10/15, natural explosion 10)
  • UI labels (Italian localization)
  • CSS class names and DOM element IDs

Algorithm Improvements

• Partition Search: Replaced recursive algorithm with iterative DFS stack-based approach
  • Improved maintainability and reasoning
  • Better memory efficiency
  • Easier to test and debug

Test Coverage

• Added 20 comprehensive regression tests covering:
  • Edge cases (empty dice, below-threshold, single die)
  • Core behavior (10-point and 15-point set formation)
  • Scoring policy (increment prioritization validation)
  • Algorithm consistency (deterministic results)

Validation

• All 20 regression tests pass (143.7ms)
• No syntax errors in any module
• 100% backward compatibility maintained
• Existing game behavior unchanged

How to Test

Run the regression test suite:

node --test tests/regression.test.mjs