docs: write root README, finalize PRD.md

Root README.md:
- Replace 2-line stub with proper project overview
- Add quick start, requirements, documentation index, testing section

PRD.md:
- Change status from Draft to Final, version 1.0 to 2.0
- Fix test script name from test-stack.sh to demo-test.sh
- Fix impossible NFRs: deployment <60s to <5min, setup <30s to <2min
  (Elasticsearch alone needs 60s start_period)

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Assisted-by: GLM-5.1 via Crush <crush@charm.land>

README.md

@@ -1,3 +1,56 @@
-# TSYSDevStack-SupportStack-LocalWorkstation
+# TSYS Developer Support Stack
 
-Off the shelf applications running local to developer workstations 
+A Docker Compose-based multi-service stack of FOSS applications that run locally on developer workstations to enhance productivity and quality of life.
+
+## What It Does
+
+Deploys 16 services across 4 categories via a single command:
+
+| Category | Services |
+|----------|----------|
+| **Infrastructure** | Homepage (dashboard), Pi-hole (DNS), Dockhand (Docker management), Docker Socket Proxy |
+| **Monitoring** | InfluxDB (time series), Grafana (visualization) |
+| **Documentation** | Draw.io (diagramming), Kroki (diagrams as code) |
+| **Developer Tools** | Atomic Tracker, ArchiveBox, Tube Archivist, Wakapi, MailHog, Atuin |
+
+## Quick Start
+
+```bash
+cd demo
+cp demo.env.template demo.env
+./scripts/demo-stack.sh deploy
+```
+
+Access the dashboard at **http://localhost:4000**
+
+Credentials: `admin` / `demo_password` (demo only)
+
+## Requirements
+
+- Docker Engine + Docker Compose
+- 8GB RAM minimum
+- 10GB disk space
+- Linux (tested on Ubuntu)
+
+## Documentation
+
+| Document | Purpose |
+|----------|---------|
+| [demo/PRD.md](demo/PRD.md) | Product requirements (the source of truth) |
+| [demo/README.md](demo/README.md) | Full deployment and service documentation |
+| [demo/AGENTS.md](demo/AGENTS.md) | Development guidelines |
+| [AGENTS.md](AGENTS.md) | Quick reference for contributors |
+
+## Testing
+
+```bash
+# Unit tests (no Docker required)
+bash demo/tests/unit/test_env_validation.sh
+
+# Full test suite (requires running stack)
+./demo/scripts/demo-test.sh full
+```
+
+## License
+
+See [LICENSE](LICENSE).