Implement core TypeScript game engine

[Spbd1]

Motivation

• Provide a pure TypeScript, framework-independent core game engine for the Parcel Society experiment that can deterministically generate maps, shocks and run simulations without Next.js or browser APIs.
• Ensure reproducible experiments by adding a seeded RNG so the same seed + config yields identical maps, shock schedules and round outcomes.
• Model the main game mechanics required by the spec: parcel generation with inequality conditions, production, player decisions, contracts, institutional uncertainty, round resolution, scoring and validation.

Description

• Added a complete engine surface and typed domain model under packages/engine/src including types.ts plus modules random.ts, gini.ts, mapGenerator.ts, production.ts, decisions.ts, contracts.ts, shocks.ts, roundResolver.ts, serverSimulator.ts, scoring.ts, and validation.ts, and exported everything from index.ts.
• Implemented deterministic seeded randomness in random.ts (SeededRandom / createRandom) and used it in mapGenerator.ts to create a 10x10 parcel grid with parcel fields (x,y,soil,water,marketAccess,risk,quality) and LOW/HIGH inequality quality mappings and a parcelQualityGini helper; added gini.ts for Gini calculation.
• Implemented the production function in production.ts with defaults (A = 10, betaQ = 0.8, betaK = 0.5) and shock multipliers; implemented deterministic shock generation and schedules in shocks.ts and contract creation/resolution and reliability computation in contracts.ts (informal vs formal fee/default risk differences).
• Implemented decision validation and application in validation.ts and decisions.ts (action points, resource cost checks, exited-player prevention, parcel ownership checks, contract fees/treasury transactions, public good payouts, investments, safe assets, lobbying, exit), deterministic institutional rule changes at rounds 3 and 5 for UNCERTAIN servers in serverSimulator.ts, a resolveRound function in roundResolver.ts that returns updated server/players/parcels/contracts/events/treasury/summary, scoring metrics in scoring.ts, and a runServerSimulation helper to run multiple rounds.
• Added Vitest unit tests in index.test.ts covering deterministic map generation, gini, production output, action-point validation, overspending checks, exited-player prevention, deterministic shock schedule, inequality Gini comparison, and a basic round resolution sanity check.

Testing

• Type-check: ran tsc --noEmit -p packages/engine/tsconfig.build.json which completed successfully for the new engine sources.
• Formatting: ran prettier --write packages/engine/src to format the new files successfully.
• Unit tests: attempted to run pnpm --filter @parcel-society/engine test (Vitest) but execution failed because node_modules are not present in this environment and vitest is unavailable; the test suite is included and will run in CI or after installing dependencies (pnpm install).
• Dependency install: attempted pnpm install but it was blocked by the environment (npm registry returned 403 Forbidden), so external tool-based checks (Vitest, ESLint) could not be executed here.

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Codex Task