updated README, added package requirements, added a test notebook.

## Summary

Adds a public roadmap and technical implementation plans to the
documentation site, giving users visibility into what's coming next for
GAIA.

## Changes

### New Documentation Pages
- **Roadmap** (`docs/roadmap.mdx`) - Timeline and upcoming priorities
- **Chat UI Plan** (`docs/plans/chat-ui.mdx` + `chat-ui.md`) -
Privacy-first desktop chat with RAG
- **Installer Plan** (`docs/plans/installer.mdx` + `installer.md`) -
Lightweight one-command installer

### Navigation Structure
Added **Roadmap** as a new top-level tab:
```
Roadmap (tab)
├── What's Next (group)
│   └── Roadmap
└── Plans (group)
    ├── Installer
    └── Chat UI
```

### Key Features
- **Q1 2026 Timeline** - Visual Mermaid diagram showing Installer → Chat
UI
- **Work in Progress label** - Transparent about evolving plans
- **Analytics-driven** - Explains how priorities are determined
- **Community engagement** - Email contact ([email protected]) for use cases
- **Dual format** - `.mdx` summaries for site, `.md` detailed specs for
GitHub

## Why

Based on analytics from amd-gaia.ai:
- `/quickstart` is the #1 page (38 views) - users want fast onboarding
- Chat agent playbook is #2 (17 views) - strong RAG/chat interest
- 60%+ Linux traffic - developer/privacy-focused audience

A public roadmap builds trust and enables community feedback on
priorities.

---------

Co-authored-by: kovtcharov-amd <[email protected]>