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/02-player/09_BPC_StaminaSystem.md

@@ -326,6 +326,41 @@ flowchart TD
 - The drain rate map supports runtime modification for buffs/debuffs (e.g. Adrenaline reduces sprint cost).
 - UI widgets should bind to OnStaminaChanged for smooth bar animation, not tick polling.
 - For multiplayer: Server authorises all DrainStamina calls; client predicts and corrects on repnotify.
+
+---
+
+## 11. Multiplayer Networking (Expanded)
+
+### Server RPCs
+
+| RPC | Direction | Description |
+|-----|-----------|-------------|
+| `Server_DrainStamina` | Client→Server | Client requests stamina drain for action. Server validates MinStamina, applies. |
+| `Server_StartContinuousDrain` | Client→Server | Client starts sprinting. Server begins drain timer. |
+| `Server_StopContinuousDrain` | Client→Server | Client stops sprinting. Server stops drain, begins regen. |
+| `Server_RestoreStamina` | Client→Server | Client uses stamina item. Server validates item, applies restore. |
+
+### Authority Gates
+
+```
+Function DrainStamina(ActionType)
+  If HasAuthority:
+    → Check cooldown, MinStamina
+    → Apply drain, update exhaustion, fire dispatchers
+  Else:
+    → Client predicts stamina bar decrease for responsiveness
+    → Server_ RPC called; server corrects via OnRep if wrong
+
+Function SetMaxStamina(NewMax, bMaintainRatio)
+  If NOT HasAuthority → Return
+  → Apply change, fire dispatchers, auto-replicates
+```
+
+### Client Prediction
+
+- **Stamina bar:** Client predicts decrease on sprint/jump. Server corrects via `OnRep_CurrentStamina`.
+- **Exhaustion:** ExhaustionState replicated. Client plays breathing audio locally.
+- **Cooldowns:** Server-authoritative. Client shows cooldown timer after server confirms action.
 - Exhaustion state can drive conditional audio: heavy breathing, heart-beat, fatigue voice lines.
 
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