feat: Add multiplayer networking architecture and documentation updates

- Updated Master Blueprint Index to include Multiplayer Networking support.
- Added detailed Multiplayer Networking sections across all developer documentation (01-11).
- Introduced authority maps, key patterns, and RPC guidelines for each system.
- Established a comprehensive multiplayer networking architecture document outlining core principles, replication strategies, and anti-cheat considerations.
- Enhanced UI documentation to clarify local-only behavior and binding to replicated dispatchers.
- Implemented client prediction strategies and RPC naming conventions for consistency across the framework.

docs/developer/architecture-overview.md

@@ -153,4 +153,45 @@ The 16 build phases follow dependency order:
 
 ---
 
+## Multiplayer Networking Architecture
+
+The framework is built server-authoritative from the ground up. See [`docs/architecture/multiplayer-networking.md`](../architecture/multiplayer-networking.md) for the full specification.
+
+### How Networking Fits the Layers
+
+```
+┌────────────────────────────────────────────────────────────────┐
+│  LOCAL-ONLY LAYER (never replicated)                            │
+│  WBP_* Widgets, Camera, Embodiment, Debug, Analytics, Tutorials │
+├────────────────────────────────────────────────────────────────┤
+│  REPLICATED STATE LAYER (server-authoritative)                  │
+│  GS_CoreGameState (chapter, objectives, encounter, time)        │
+│  Player Components (health, stamina, stress, movement, hide)    │
+│  World Actors (doors, containers, pickups, puzzles)             │
+│  Inventory (slots, weight, equipment)                           │
+│  Narrative (flags, dialogue state, objectives)                  │
+│  AI (position, alert state, health — behavior trees on server)  │
+│  Adaptive (atmosphere tier, tension, difficulty params)         │
+├────────────────────────────────────────────────────────────────┤
+│  CLIENT PREDICTION LAYER (cosmetic, corrected by server)        │
+│  Weapon fire FX, muzzle flash, recoil, hit markers              │
+│  Stamina bar, health bar (predicted; RepNotify corrects)        │
+│  Door animations (predicted; OnRep confirms)                    │
+├────────────────────────────────────────────────────────────────┤
+│  SERVER-ONLY LAYER                                              │
+│  AI Behavior Trees, Damage Calculation, Loot Generation         │
+│  Save/Load coordination, State Gating validation                │
+└────────────────────────────────────────────────────────────────┘
+```
+
+### Key Multiplayer Principles
+1. **HasAuthority() gate** on every mutator function
+2. **Server_ RPC** for client→server requests
+3. **RepNotify** fires same dispatchers as SP code — UI needs zero changes
+4. **Client prediction** for responsiveness; server correction for correctness
+5. **AI runs on server** only — replicated to clients via Actor replication
+6. **UI is local per-client** — binds to replicated dispatchers
+
+---
+
 *Architecture Overview v1.0 — Start here before reading category-specific developer docs.*