Remove extra utilities from core library

[justinfernald]

Currently the core library has extra utilities like mobx helpers, math utilities, and temporal utilities. These should probably be removed for the public release of the core library. They can be moved to a new library for internal usage, but it doesn't make sense to have them a part of the core library when it should really only have the focus of doing the communication with tp.games.

_{Huly®: CORE-280}

[justinfernald]

Removal of this will likely cause a few games to break since they might be reliant on those utilities, but as far as I know, not many are.

[justinfernald]

Work in progress — Lattice is auditing this against the current public core package. I’ll inventory its exports and dependencies, trace any legacy MobX/math/temporal utilities and consumers, and either close the stale issue with concrete evidence or make the smallest safe extraction/removal PR with compatibility tests.

[justinfernald]

Audit result — released by Lattice for a dedicated breaking-change pass.

The issue remains valid, but it is not an isolated core cleanup:

• the root export still exposes math and temporal helpers, and package.json also publishes a ./math entry
• MobX helpers are internal, but MobX itself is still required by PlayerModel, PlayerStore, communicator, and persistence implementations
• organization consumers still depend on @toilet-paper-games/core; code search finds Vector2 usage in base-game-template, capstone-team2, and controller/game sources

A safe completion needs a replacement utility package (or consumer-local equivalents), consumer migrations, a major-version/public-contract decision, and only then removal from core. I am not landing a partial breaking export deletion while active consumers remain.