Add shared utilities: Result, assert, deepEqual, common types, log

Foundational helpers referenced by most subsequent code. Small, pure,
no dependencies on anything in the project.

  utils/result.ts   Result<T, E> = Ok<T> | Err<E> for recoverable
                    failures at system boundaries (save/load, manifest
                    fetch, content validation). Internal pure logic
                    still uses throw for programmer errors.
                    ok / err / isOk / isErr / mapResult / mapErr /
                    unwrap / unwrapOr.
  utils/assert.ts   assert (with type-narrowing asserts), assertNever
                    for exhaustive-switch termination, assertDefined
                    for narrowing T | null | undefined → T.
  utils/equal.ts    Structural deepEqual for tests comparing simulation
                    snapshots. Handles plain objects, arrays, Map, Set,
                    Date, primitives. Does not handle cyclic graphs
                    (simulation state is a tree).
  utils/types.ts    Common type aliases: NonEmptyArray, JsonValue,
                    ElementOf, DeepReadonly, Brand<T, B> for nominal /
                    branded types (PersonId vs RelationshipId).
  utils/log.ts      Structured logging wrapping console. Developer-
                    facing only; the game ships with no runtime
                    telemetry.
  utils/index.ts    Public re-exports.

40 unit tests in tests/unit/utils/ cover Result constructors and
combinators, assert variants, and deepEqual's primitive / array /
object / Map / Set / Date paths plus a realistic simulation-snapshot
comparison.

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