Add Project Prototype Guide for PG_Framework Testing Setup

- Introduced a comprehensive guide for creating a minimal playable prototype in UE5.
- Detailed steps for project creation, C++ module integration, gameplay tags setup, and player pawn assembly.
- Included instructions for input system setup, state management wiring, and test level setup.
- Provided a verification checklist and troubleshooting section to assist developers.
- Documented next steps for expanding the prototype with additional systems.

docs/blueprints/INDEX.md

@@ -1,9 +1,18 @@
 # Master Blueprint Index — UE5 Modular Game Framework
 
-**Version:** 3.2 | **Generated:** 2026-05-20 | **Total Files:** 135 numbered + 1 starter + 1 supplementary (137 total specs)
+**Version:** 3.3 | **Generated:** 2026-05-21 | **Total Files:** 135 numbered + 1 starter + 1 supplementary (137 total specs) | **C++:** 22 source files
 
 This document is the canonical index of every Blueprint specification file in the framework. Each entry links to its full spec document and includes: file name, asset type, parent class, purpose summary, and key dependencies.
 
+### Companion Documents
+
+| Document | Path | Purpose |
+|----------|------|---------|
+| **Remaining BP Build Order** | [`../checklists/remaining-blueprint-build-order.md`](../checklists/remaining-blueprint-build-order.md) | Prioritized list of every BP asset to build, with C++ status per system |
+| **C++/BP Status Grid** | [`../checklists/cpp-blueprint-status.md`](../checklists/cpp-blueprint-status.md) | Complete 135-system grid: C++ status, BP spec status, remaining assets |
+| **C++ Integration Guide** | [`../developer/cpp-integration-guide.md`](../developer/cpp-integration-guide.md) | Per-C++-class setup steps, usage patterns, BP child requirements |
+| **Prototype Setup Guide** | [`../developer/project-prototype-guide.md`](../developer/project-prototype-guide.md) | Step-by-step from blank project to working prototype |
+
 ---
 
 ## Directory Map