Split Rust game src into modules; update AGENTS.md for dual toolchain

- Refactor apps/game/src/main.rs into modules: state.rs, camera.rs, ui/, gameplay/
- Add gameplay/galaxy_creation.rs scaffold (stubs only, no new logic)
- Update root AGENTS.md: separate TS workspace vs Rust game commands
- Update apps/AGENTS.md: docs/game/site use two toolchains, not one
- Add apps/game/AGENTS.md: build commands, module layout, naming conventions, Plugin pattern

AGENTS.md

@@ -6,37 +6,54 @@ Single-player open-world space exploration RPG. Windward Horizon in space with F
 
 | Path | Purpose |
 |------|---------|
-| `apps/docs` | Living design docs, interactive demos, and vertical-slice prototype |
-| `apps/game` | Playable game shell connected to SpacetimeDB |
-| `apps/site` | Public landing page |
-| `packages/ui` | Shared UI primitives and design tokens |
-| `services/spacetimedb` | SpacetimeDB TypeScript backend module |
+| `apps/docs` | Living design docs, interactive demos, and vertical-slice prototype (Vite + React) |
+| `apps/game` | Playable game client — **Rust + Bevy** (independent of the JS/TS workspace) |
+| `apps/site` | Public landing page (Vite + React) |
+| `packages/ui` | Shared UI primitives and design tokens for the TS apps |
+| `services/spacetimedb` | SpacetimeDB TypeScript backend module (authoritative game state) |
 | `scripts/` | Dev tooling (dev.sh startup script) |
 | `archive/` | Legacy pre-monorepo files kept for reference |
-| `src/module_bindings/` | Empty; generated bindings go to `apps/game/src/module_bindings` |
 
 ## Key Files
 
 - `package.json` — pnpm workspace scripts (`dev`, `build`, `check`, `generate:bindings`)
-- `pnpm-workspace.yaml` — workspace glob patterns
+- `pnpm-workspace.yaml` — workspace glob patterns (covers TS apps only)
 - `spacetime.json` — SpacetimeDB module path and binding generation config
-- `tsconfig.base.json` — Shared TypeScript config (ES2020, React JSX)
+- `tsconfig.base.json` — Shared TypeScript config (ES2020, React JSX) — does not apply to `apps/game`
+- `apps/game/Cargo.toml` — Rust manifest for the game binary
 
 ## Commands
 
+### JS/TS workspace (docs, site, packages/ui, services)
+
 ```bash
-pnpm dev                # Full stack: SpacetimeDB + game (port 5175)
+pnpm dev                # Full stack: SpacetimeDB + docs/site
 pnpm dev:docs           # Docs only (port 5173)
 pnpm dev:site           # Site only (port 5174)
-pnpm dev:game           # Game frontend only (requires running SpacetimeDB)
-pnpm build              # Build all apps
-pnpm check              # Typecheck all packages
+pnpm build              # Build all TS packages
+pnpm check              # Typecheck all TS packages
 pnpm generate:bindings  # Regenerate SpacetimeDB TypeScript bindings
 ```
 
-## Conventions
+### Rust game (`apps/game`)
 
-- SpacetimeDB is the persistence layer from day 1 — no localStorage for game state
-- All UI uses Tailwind CSS v4 with custom design tokens from `packages/ui`
-- 3D rendering uses React Three Fiber + Drei + Three.js
-- Module bindings are auto-generated — never edit `module_bindings/` by hand
+```bash
+cd apps/game
+cargo run               # Build + run the game binary
+cargo check             # Fast typecheck
+cargo build             # Build without running
+cargo clippy            # Lint
+```
+
+## Architecture Notes
+
+- **Two independent toolchains coexist**: the pnpm/TS workspace (docs, site, UI lib, SpacetimeDB backend) and the Cargo/Rust game client. They share no code.
+- **SpacetimeDB** remains the authoritative persistence layer. The game client will connect to it via the SpacetimeDB Rust SDK when wired up (TS bindings generated by `pnpm generate:bindings` are consumed by the docs prototype, not the game).
+- **Naming follows RFC 344**: see `apps/game/AGENTS.md` for Rust/Bevy conventions.
+
+## Conventions (TS apps)
+
+- SpacetimeDB is the persistence layer from day 1 — no localStorage for game state in the docs prototype
+- TS apps use Tailwind CSS v4 with custom design tokens from `packages/ui`
+- 3D rendering in `apps/docs` uses React Three Fiber + Drei + Three.js
+- Module bindings are auto-generated — never edit generated bindings by hand