Set up DOTS + Netcode for Entities foundation

One-time stack setup per Docs/dots-setup-task.md (Unity 6.4.7 / 6000.4.7f1).
Packages: entities 6.4.0, entities.graphics 6.4.0, netcode 1.13.2, physics 1.4.6.

- Assets/_Project asmdef split: ProjectM.Simulation/Client/Server/Authoring (root ns ProjectM)
- GameBootstrap : ClientServerBootstrap; verified separate client + server worlds in Play Mode
- Gameplay subscene wired into SampleScene as a baking target
- Heartbeat component + Burst ISystem; EditMode smoke test green (1/1)
- In-repo Obsidian vault (Docs/Vault) incl. DR-001 (plain-Entities test over internal NetCodeTestWorld)
- Portable .mcp.json (basic-memory + serena via ${CLAUDE_PROJECT_DIR}); CLAUDE.md conventions
- .gitignore for DOTS baking cache + machine-local config

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Docs/Vault/02_Game_Design/Systems_Index.md

@@ -0,0 +1,19 @@
+---
+tags:
+- design
+- index
+updated: 2026-05-29
+permalink: gamevault/02-game-design/systems-index
+---
+
+# Systems Design — Index
+
+One design doc per gameplay system, linked here. Each should state: purpose, components (`IComponentData`), systems (`ISystem`), netcode shape (ghost? predicted vs interpolated? inputs / RPCs), and open questions.
+
+## Systems
+
+- _None yet._
+
+## Conventions
+
+DOTS/ECS conventions live in repo `CLAUDE.md` and the `dots-dev` skill's `dots-conventions.md`. Don't duplicate volatile API details here — link to context7-derived notes instead.