docs: update README.md with DAG validator, catalog loader, and 100+ product scaling guide

README.md

@@ -21,10 +21,16 @@ The game is packaged as a lightweight, turnkey **Docker Compose stack** powered
     1. **Agriculture & Food:** Wheat, Milled Flour, Sugar Beet, Refined Sugar, Artisan Bread, Packaged Meals.
     2. **Forestry & Materials:** Raw Timber, Milled Planks, Industrial Paper, Office Furniture.
     3. **Mining & Metallurgy:** Iron Ore, Coking Coal, Structural Steel, Heavy Frameworks.
-    4. **Chemicals & Polymers:** Crude Oil, Silica Quartz Sand, Industrial Polymers, Purified Silicon.
+    4. **Chemicals & Polymers:** Crude Oil, Silica Quartz Sand, Industrial Polymers, Purified Silicon, Industrial Fertilizer.
     5. **High-Tech & Electronics:** Silicon Microchips, PCB Motherboards, Consumer Smartphones.
     6. **Heavy Industry & Vehicles:** Industrial Engines, Commercial Logistics Trucks.
 
+* **Modular "Plug & Play" Product Architecture (Scale to 100+ Products):**
+  * Sector manifests are stored as self-contained ES-module catalog files under `frontend/js/data/sectors/*.js`.
+  * **Single Source of Truth:** The Python FastAPI backend dynamically parses and registers sector files on startup (`backend/catalog_loader.py`), keeping frontend and backend simulation logic 100% in sync without duplicated configurations.
+  * Creating a new sector or adding 10, 50, or 100+ new units requires simply dropping a new sector file or object into `frontend/js/data/sectors/` and adding matching photos.
+  * See [`PRODUCT_GENERATOR_GUIDE.md`](./PRODUCT_GENERATOR_GUIDE.md) for complete manifest schemas, AI generator prompts, and instructions for bulk-adding products and sectors.
+
 * **Dedicated Facility Intelligence Dossier (Unit Detail View):**
   * Clicking any facility card opens a comprehensive, full-page analytics dossier tailored for data and numbers enthusiasts.
   * **Financial Telemetry:** Wholesale unit price, live revenue/s, projected revenue/hour, asset valuation, and stock inventory value.
@@ -108,12 +114,18 @@ docker compose up -d --build
 The game is live in your browser at:  
 👉 **`http://localhost:8081`** (or the port defined in `.env`).
 
-### 4. Running Backend Verification Tests
+### 4. Running Verification & DAG Validation
-To run the automated Python backend engine simulation tests:
+To run the automated backend engine simulation tests:
 ```bash
 python backend/test_engine.py
 ```
 
+To run the automated supply chain integrity and DAG validator:
+```bash
+python backend/validate_dag.py
+```
+*(Verifies cycle-free graphs, valid input/output dependencies, positive tier-margin economics, and file reference consistency across all modular sectors.)*
+
 ---
 
 ## 📁 Project Directory Structure
@@ -122,16 +134,19 @@ python backend/test_engine.py
 .
 ├── .env.example
 ├── docker-compose.yml
-├── FACILITY_PHOTO_PROMPT_GUIDE.md  # Photographic generation guide for all 24 units & goods
+├── FACILITY_PHOTO_PROMPT_GUIDE.md  # Photographic generation guide for units & goods
+├── PRODUCT_GENERATOR_GUIDE.md      # AI prompt & schema guide for scaling to 100+ products
 ├── backend/
 │   ├── Dockerfile
 │   ├── requirements.txt
 │   ├── auth.py              # JWT authentication & password hashing
+│   ├── catalog_loader.py   # Dynamic loader for modular frontend sector files
 │   ├── database.py          # SQLite connection and migration setup
 │   ├── engine.py            # Authoritative DAG simulation and offline calculations
 │   ├── main.py              # FastAPI endpoints
 │   ├── models.py            # Pydantic schemas
-│   └── test_engine.py       # Comprehensive backend regression test suite
+│   ├── test_engine.py       # Comprehensive backend regression test suite
+│   └── validate_dag.py      # Automated DAG integrity, cycle & margin validator
 ├── frontend/
 │   ├── index.html           # Full-width executive workspace layout
 │   ├── assets/
@@ -161,8 +176,8 @@ python backend/test_engine.py
 │       │   ├── state.js     # State manager, schema handling & IPO reset
 │       │   └── sync.js      # Backend synchronization & auth handling
 │       ├── data/
-│       │   ├── products.js  # 24+ commodities across 6 sectors
+│       │   ├── products.js  # Central re-exporter of modular sectors
-│       │   ├── sectors/     # Modular sector & product definitions
+│       │   ├── sectors/     # Modular sector & product definitions (Agriculture, etc.)
 │       │   ├── contracts.js # B2B procurement tenders
 │       │   ├── boardroom.js # IPO perks and Venture Share logic
 │       │   └── achievements.js
@@ -184,4 +199,5 @@ python backend/test_engine.py
 
 ## 🎨 Asset Generation & Custom Visuals
 
-Refer to [`FACILITY_PHOTO_PROMPT_GUIDE.md`](./FACILITY_PHOTO_PROMPT_GUIDE.md) for master prompts and camera recipes to generate photorealistic assets for all 24 production facilities and commodities using modern image models (Midjourney, Stable Diffusion, Imagen). Dropping generated images into `frontend/assets/images/facilities/` and `frontend/assets/images/products/` seamlessly populates the facility dossiers without modifying any code.
+* Refer to [`FACILITY_PHOTO_PROMPT_GUIDE.md`](./FACILITY_PHOTO_PROMPT_GUIDE.md) for master prompts and camera recipes to generate photorealistic assets for production facilities and commodities using modern image models (Midjourney, Stable Diffusion, Imagen). Dropping generated images into `frontend/assets/images/facilities/` and `frontend/assets/images/products/` seamlessly populates the facility dossiers without modifying any code.
+* Refer to [`PRODUCT_GENERATOR_GUIDE.md`](./PRODUCT_GENERATOR_GUIDE.md) when generating new products, supply chain DAG tiers, or entire industry sectors.