Refactor GameplayTag documentation and implementation

- Updated references from GI_GameTagRegistry to DA_GameTagRegistry in architecture overview and implementation patterns documentation.
- Added new Blueprint specification for GI_StarterGameInstance, detailing its purpose, configuration, and integration pattern.
- Introduced DA_GameTagRegistry Blueprint specification, centralizing GameplayTag management and providing functions for tag validation and logging.
- Created documentation for the Starter GameInstance, outlining its role in the project setup and how other systems can integrate with it.

docs/developer/INDEX.md

@@ -1,6 +1,6 @@
 # Developer Reference — UE5 Modular Game Framework
 
-**Version:** 1.2 | **Generated:** 2026-05-19 | **Files:** 15 (1 index + 2 overview + 1 migration + 10 category docs + 1 combined) | **Networking:** All docs include multiplayer sections
+**Version:** 1.3 | **Generated:** 2026-05-20 | **Files:** 16 (1 index + 2 overview + 1 migration + 1 starter + 10 category docs + 1 combined) | **Networking:** All docs include multiplayer sections
 
 This directory contains developer-facing reference documentation for every system in the framework. Unlike the blueprint spec files (which define *what* to build), these documents explain *how each system works internally* — the data flow, state machines, integration points, and design rationale. Use these when you need to understand a system's behavior to implement, debug, or extend it.
 
@@ -21,6 +21,7 @@ docs/developer/
 ├── project-setup-migration.md            ← Project setup & migration guide (NEW — Project Settings, plugins, init sequence)
 │
 ├── 01-core-foundation.md                 ← Foundation systems (systems 01-07)
+├── 00-starter-gameinstance.md            ← Starter GameInstance: GI_StarterGameInstance setup guide
 ├── 02-player-systems.md                  ← Player state & embodiment (systems 08-15)
 ├── 03-interaction-systems.md             ← Interaction & world manipulation (systems 16-23)
 ├── 04-inventory-systems.md               ← Inventory, items & collectibles (systems 24-34)
@@ -37,7 +38,8 @@ docs/developer/
 
 | # | System | Category | Role |
 |---|--------|----------|------|
-| 01 | `GI_GameTagRegistry` | Foundation | Central GameplayTag → asset registry |
+| — | `GI_StarterGameInstance` | Project Setup | Minimal GameInstance; tag validation entry point |
+| 01 | `DA_GameTagRegistry` | Foundation | Central GameplayTag → asset registry |
 | 02 | `FL_GameUtilities` | Foundation | Shared utility functions (logging, math) |
 | 03 | `I_InterfaceLibrary` | Foundation | All framework interfaces |
 | 04 | `GI_GameFramework` | Foundation | Application kernel; owns subsystems |
@@ -176,7 +178,7 @@ docs/developer/
 ## How to Use These Docs
 
 1. **New to the framework?** Start with [`architecture-overview.md`](architecture-overview.md) to understand the big picture.
-2. **Setting up a new project?** Read [`project-setup-migration.md`](project-setup-migration.md) — covers all Project Settings, plugins, Data Tables, Enhanced Input, and initialization sequence.
+2. **Setting up a new project?** Read [`00-starter-gameinstance.md`](00-starter-gameinstance.md) first — create `GI_StarterGameInstance` to validate your GameplayTags immediately. Then follow [`project-setup-migration.md`](project-setup-migration.md) for full Project Settings, plugins, Data Tables, and init sequence.
 3. **Implementing a system?** Read the Blueprint Spec in `docs/blueprints/` — every file has a Manual Implementation Guide with node-by-node logic.
 4. **Need to understand internals?** Read the corresponding Developer Reference doc in this directory.
 5. **Debugging?** Each category doc includes a data flow section showing how data moves between systems.