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/blueprints/03-interaction/16_BPC_InteractionDetector.md

@@ -379,4 +379,29 @@ flowchart TD
 
 ---
 
+## 11. Multiplayer Networking (Expanded)
+
+### Replication
+| Variable | Condition | Purpose |
+|----------|-----------|---------|
+| `CurrentTarget` | `Replicated` | Synced target for UI (other players see what you're looking at) |
+
+### Server RPCs
+| RPC | Direction | Description |
+|-----|-----------|-------------|
+| `Server_PerformInteraction` | Client→Server | Client requests interaction. Server validates range, conditions, then calls I_Interactable. |
+
+### Authority
+- **Detection** (trace, sorting, target selection): runs locally per client.
+- **Interaction execution**: server-authoritative. Client calls `Server_PerformInteraction`; server validates and executes.
+- `ForceSetTarget`: server-only for scripted interactions.
+- `HighlightTarget`: local cosmetic effect per client.
+
+### Client Prediction
+- Interaction prompt: shown immediately based on local trace.
+- Hold progress: shown locally; server confirms completion.
+- Blocked feedback: shown locally if conditions fail client-side; server may also reject.
+
+---
+
 *Blueprint Spec: Interaction Detector. Conforms to TEMPLATE.md v1.0 — part of the UE5 Modular Game Framework.*

docs/blueprints/03-interaction/17_I_HidingSpot.md

@@ -283,4 +283,26 @@ sequenceDiagram
 
 ---
 
+## 10. Multiplayer Networking
+
+### Replicated Variables
+| Variable | Condition | Purpose |
+|----------|-----------|---------|
+| `bOccupied` | `Replicated` | Other clients see spot as occupied |
+| `LockedByPlayer` | `Replicated` | Synced lock state |
+| `OccupantPawn` | `Replicated` | Who is hiding here (for third-person visibility) |
+| `bIsVisible` | `Replicated` | Spot availability synced |
+
+### Authority
+- `OnPlayerEntered`/`OnPlayerExited` are called by the server-authoritative `BPC_HidingSystem`.
+- `LockSpot`/`UnlockSpot` are server-only.
+- `GetOccupancyStatus` is read-only, safe for any side.
+
+### Server RPCs
+| RPC | Direction | Description |
+|-----|-----------|-------------|
+| `Server_ClaimSpot` | Client→Server | Client requests occupying spot. Server validates availability. |
+
+---
+
 *Blueprint Spec: Hiding Spot Interface & Actor. Conforms to TEMPLATE.md v1.0 — part of the UE5 Modular Game Framework.*

docs/blueprints/03-interaction/19_BP_DoorActor.md

@@ -336,4 +336,38 @@ Player Presses Interact
 
 - This renamed file (formerly `BPC_InteractableDoorComponent`) is now an Actor-based system (`BP_DoorActor`) as per Master Section 3.5.
 - The door actor encapsulates all door logic directly rather than as an ActorComponent.
-- Cross-references updated: `BPC_InventoryComponent` → `BPC_InventorySystem`, `BPC_LeverPuzzleComponent` → `BP_PuzzleDeviceActor`.
+- Cross-references updated: `BPC_InventoryComponent` → `BPC_InventorySystem`, `BPC_LeverPuzzleComponent` → `BP_PuzzleDeviceActor`.
+
+---
+
+## 13. Multiplayer Networking (Expanded)
+
+### Server RPCs
+
+| RPC | Direction | Description |
+|-----|-----------|-------------|
+| `Server_Interact` | Client→Server | Client requests door interaction. Server validates range, state, lock, then executes TryOpen/TryClose. |
+| `Server_DamageBarricade` | Client→Server | Client deals damage to barricade. Server validates damage source, applies to barricade health. |
+| `Server_TryUnlock` | Client→Server | Client attempts unlock with key item. Server validates inventory, consumes item if configured. |
+
+### Authority Gates
+
+```
+Interact_Implementation
+  If NOT HasAuthority:
+    → Call Server_Interact(DoorActor)
+    → Return (client prediction: show prompt, wait for OnRep)
+  // Server executes authoritative logic
+  → TryOpen / TryClose / TryUnlock
+  → OnRep broadcasts to all clients
+```
+
+### Client Prediction
+- **Interaction:** Client calls `Server_Interact` RPC; server validates and changes state.
+- **Animation:** `OnRep_DoorState` triggers animation on all clients identically.
+- **Locked feedback:** Played locally by client when server rejects interaction.
+
+### Anti-Cheat
+- Server validates player is within interaction range before opening door.
+- Server validates key item is in player inventory before unlocking.
+- Server validates barricade damage source.