Fix ESLint errors in test files and source code

[Copilot]

Resolved 18 ESLint errors across test and source files identified by the linter.

Changes

• audio-system.test.ts: Replaced any types with MockHowl interface for type-safe mock objects

  interface MockHowl {
    play: () => void;
  }
  
  const audioComponent: AudioEcsComponent = {
    sound: { play: mockPlay } as MockHowl,  // was: as any
    playSound: true,
  };

• transform-system.ts: Extracted setTransformsToLocal and applyParentTransforms helper functions to reduce cognitive complexity from 29 to under threshold (15)

• particle-emitter-system.test.ts: Added assertion to verify no particles created when emitter is empty

• render-system.ts: Removed commented-out scissor test code

• game.ts: Reordered class members to comply with member-ordering rules (public fields before private)

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