Initialize League GUI prototype

INSTALL.md

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+# Installation
+
+This guide explains how to install and run the League of Legends GUI Overhaul prototype locally.
+
+The project is a React/Vite/TypeScript app. It does not install a game client, connect to Riot services, or include official Riot assets.
+
+## Requirements
+
+- Node.js with npm available in your terminal.
+- Recommended npm version: 10 or newer.
+- A local clone of this repository.
+
+Check your tools:
+
+```powershell
+node --version
+npm --version
+```
+
+## Install Dependencies
+
+Open a terminal in this project folder:
+
+```powershell
+cd D:\Codex\Main\CodexTest\projects\league-of-legends-gui-overhaul
+```
+
+Install dependencies:
+
+```powershell
+npm install
+```
+
+This creates `node_modules/` locally. The folder is ignored by Git.
+
+## Start The GUI
+
+Start the local development server:
+
+```powershell
+npm run dev
+```
+
+Vite prints a local URL, usually:
+
+```text
+http://localhost:5173
+```
+
+Open that URL in your browser.
+
+## Verify The Installation
+
+Run the production build:
+
+```powershell
+npm run build
+```
+
+Run the test suite:
+
+```powershell
+npm test
+```
+
+Optional dependency audit:
+
+```powershell
+npm audit --audit-level=moderate
+```
+
+## Preview A Production Build
+
+After `npm run build`, preview the built app:
+
+```powershell
+npm run preview
+```
+
+## Common Problems
+
+### `npm` is not recognized
+
+Install Node.js from the official Node.js distribution or add an existing Node/npm installation to your `PATH`.
+
+After updating `PATH`, open a new terminal and check again:
+
+```powershell
+npm --version
+```
+
+### Port 5173 is already in use
+
+Start Vite on another port:
+
+```powershell
+npm run dev -- --port 5174
+```
+
+### Dependencies changed
+
+If `package-lock.json` changed or dependencies were updated, reinstall:
+
+```powershell
+npm install
+```
+
+## What This Installs
+
+The install step only installs frontend development dependencies for this prototype:
+
+- React
+- Vite
+- TypeScript
+- React Router
+- Vitest
+- Testing Library
+
+It does not install any Riot software, game files, launchers, or protected assets.