Extract weekly polling resolution into the pure simulation layer

[aribradshaw]

Goal

Reduce the contributor cost of changing weekly polling without destabilizing the campaign facade.

Suggested boundary

Extract one polling-resolution phase from GameEngine.ts into a pure function under src/game/simulation/. Accept immutable state, planned actions, and an injected random source. Return the next polling state plus explanatory deltas for the weekly recap.

Acceptance criteria

• No global Math.random() is introduced.
• Input maps are not mutated.
• Existing campaign outcomes remain inside documented calibration bounds.
• Focused determinism, bounds, and no-NaN tests are added.
• GameEngine delegates to the new function.