Initial public release of PSX Adventure Engine

Browser reference stack for PSX-era third-person adventure: fixed cameras,
inventory puzzles, Box3D physics, host-authoritative P2P co-op, and a modular
character harness. Ships the Ashgrove Precinct Level 1 investigation demo with
a full cast and nine linked rooms.

CONTRIBUTING.md

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+# Contributing
+
+Thanks for looking at the project. A few conventions keep the monorepo tidy.
+
+## Setup
+
+```bash
+pnpm install
+pnpm typecheck
+pnpm test
+```
+
+## Packages
+
+| Package | Responsibility |
+| --- | --- |
+| `client` | Game runtime (must stay free of Node-only APIs) |
+| `server` | Auth, lobbies, signalling |
+| `shared` | Types and schemas used by both ends |
+| `tools` | Character pipeline (Node only) |
+
+Put new gameplay types in `shared` before wiring them into client/server.
+
+## Style
+
+- TypeScript strict; no `any` without a comment why.
+- Prefer small declarative room / item / cast data over one-off engine forks.
+- Keep PSX constraints intentional: low poly, fixed cams, fog, nearest textures.
+
+## Pull requests
+
+1. One concern per PR when possible.
+2. `pnpm typecheck && pnpm test` green.
+3. Update `README.md` / `GDD.md` when behaviour or demo layout changes.
+
+## Character assets
+
+Prefer `pnpm cast` / the creator UI over hand-editing GLBs. Ship
+`assets/characters/{id}.glb` plus `.recipe.json` (and albedo if textured).
+Do not commit `.grok-texture-cache` or `*.analysis.json`.