Update README with comprehensive project documentation

Added complete project overview including:
- Tech stack and architecture overview
- Quick start guide with UV and Pulumi ESC setup
- Project structure (extract, transform, core packages)
- Development workflow (dependencies, linting, testing)
- Secrets management with ESC examples
- Production architecture explanation
- Architecture principles

Removed outdated content and references to CLAUDE.md (internal memory only).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

README.md

@@ -1,39 +1,181 @@
-# Materia Environment Setup
+# Materia
 
-We use `uv` as our Python package manager for faster, more reliable dependency management.
-https://docs.astral.sh/uv/
+A commodity data analytics platform built on a modern data engineering stack. Extracts agricultural commodity data from USDA PSD Online, transforms it through a layered SQL pipeline using SQLMesh, and stores it in DuckDB + Cloudflare R2 for analysis.
 
-We recommend using vscode as your IDE.
-https://code.visualstudio.com/
+## Tech Stack
+
+- **Python 3.13** with `uv` package manager
+- **SQLMesh** for SQL transformation and orchestration
+- **DuckDB** as the analytical database
+- **Cloudflare R2** (Iceberg) for data storage
+- **Pulumi ESC** for secrets management
+- **Hetzner Cloud** for infrastructure
+
+## Quick Start
 
 ### 1. Install UV
 
+UV is our Python package manager for faster, more reliable dependency management.
+
 ```bash
 curl -LsSf https://astral.sh/uv/install.sh | sh
 ```
 
-### 2. Setup the env
-Simply run:
+📚 [UV Documentation](https://docs.astral.sh/uv/)
+
+### 2. Install Dependencies
 
 ```bash
 uv sync
 ```
-This will install python & the dependencies declared so far
 
-### 3. Setup pre-commit
+This installs Python and all dependencies declared in `pyproject.toml`.
+
+### 3. Setup Pre-commit Hooks
+
 ```bash
 pre-commit install
 ```
 
-### 4. Adding a dependency
+This enables automatic linting with `ruff` on every commit.
+
+### 4. Install Pulumi ESC (for running with secrets)
 
 ```bash
-uv add requests
+# Install ESC CLI
+curl -fsSL https://get.pulumi.com/esc/install.sh | sh
+
+# Login
+esc login
 ```
 
-# Managing a project with uv
+## Project Structure
 
-https://docs.astral.sh/uv/guides/projects/#managing-dependencies
+This is a `uv` workspace with three main packages:
 
+### Extract Layer (`extract/`)
 
-test
+**psdonline** - Extracts USDA PSD commodity data
+
+```bash
+# Local development (downloads to local directory)
+uv run extract_psd
+
+# Production (uploads to R2)
+esc run beanflows/prod -- uv run extract_psd
+```
+
+### Transform Layer (`transform/sqlmesh_materia/`)
+
+SQLMesh project implementing a 4-layer data architecture (raw → staging → cleaned → serving).
+
+**All commands run from project root with `-p transform/sqlmesh_materia`:**
+
+```bash
+# Local development
+esc run beanflows/prod -- uv run sqlmesh -p transform/sqlmesh_materia plan dev_<username>
+
+# Production
+esc run beanflows/prod -- uv run sqlmesh -p transform/sqlmesh_materia plan prod
+
+# Run tests (no secrets needed)
+uv run sqlmesh -p transform/sqlmesh_materia test
+
+# Format SQL
+uv run sqlmesh -p transform/sqlmesh_materia format
+```
+
+### Core Package (`src/materia/`)
+
+CLI for managing infrastructure and pipelines (currently minimal).
+
+## Development Workflow
+
+### Adding Dependencies
+
+For workspace root:
+```bash
+uv add <package-name>
+```
+
+For specific package:
+```bash
+uv add --package psdonline <package-name>
+```
+
+### Linting and Formatting
+
+```bash
+# Check for issues
+ruff check .
+
+# Auto-fix issues
+ruff check --fix .
+
+# Format code
+ruff format .
+```
+
+### Running Tests
+
+```bash
+# Python tests
+uv run pytest tests/ -v --cov=src/materia
+
+# SQLMesh tests
+uv run sqlmesh -p transform/sqlmesh_materia test
+```
+
+## Secrets Management
+
+All secrets are managed via **Pulumi ESC** environment `beanflows/prod`.
+
+### Load secrets into shell:
+
+```bash
+eval $(esc env open beanflows/prod --format shell)
+```
+
+### Run commands with secrets:
+
+```bash
+# Single command
+esc run beanflows/prod -- uv run extract_psd
+
+# Multiple commands
+esc run beanflows/prod -- bash -c "
+  uv run extract_psd
+  uv run sqlmesh -p transform/sqlmesh_materia plan prod
+"
+```
+
+## Production Architecture
+
+### Git-Based Deployment
+
+- **Supervisor** (Hetzner CPX11): Always-on orchestrator that pulls latest code every 15 minutes
+- **Workers** (Ephemeral): Created on-demand for each pipeline run, destroyed after completion
+- **Storage**: Cloudflare R2 Data Catalog (Apache Iceberg REST API)
+
+### CI/CD Pipeline
+
+**GitLab CI** runs on every push to master:
+
+1. **Lint** - `ruff check`
+2. **Test** - pytest + SQLMesh tests
+3. **Deploy** - Updates supervisor infrastructure and bootstraps if needed
+
+No build artifacts - supervisor pulls code directly from git!
+
+## Architecture Principles
+
+- **Simplicity First** - Avoid unnecessary abstractions
+- **Data-Oriented Design** - Identify data by content, not metadata
+- **Cost Optimization** - Ephemeral workers, minimal always-on infrastructure
+- **Inspectable** - Easy to understand, test locally, and debug
+
+## Resources
+
+- **Architecture Plans**: See `.claude/plans/` for design decisions
+- **UV Docs**: https://docs.astral.sh/uv/
+- **SQLMesh Docs**: https://sqlmesh.readthedocs.io/