Rebuild website from scratch on Tailwind v4 + shadcn/ui

- Fresh Astro 5 project with Tailwind v4 and shadcn/ui olive preset
- All shadcn components installed (Card, Button, Badge, Separator, etc.)
- Homepage with hero, terminal demo, workflows, agents, sources, compute
- Full docs system with 24 markdown pages across 5 sections
- Sidebar navigation with active state highlighting
- Prose styles for markdown content using shadcn color tokens
- Dark/light theme toggle with localStorage persistence
- Shiki everforest syntax themes for code blocks
- 404 page with VT323 font
- /docs redirect to installation page
- GitHub star count fetch
- Earthy green/cream oklch color palette matching TUI theme

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

website/src/content/docs/getting-started/installation.md

@@ -1,44 +1,69 @@
 ---
 title: Installation
-description: Install Feynman and get started
+description: Install Feynman on macOS, Linux, or Windows using the one-line installer or npm.
 section: Getting Started
 order: 1
 ---
 
-## Requirements
+Feynman ships as a standalone binary for macOS and Linux, and as an npm package for all platforms including Windows. The recommended approach is the one-line installer, which downloads a prebuilt native binary with zero dependencies.
 
-- macOS, Linux, or WSL
-- `curl` or `wget`
+## One-line installer (recommended)
 
-## Recommended install
+On **macOS or Linux**, open a terminal and run:
 
 ```bash
 curl -fsSL https://feynman.is/install | bash
 ```
 
-## Verify
+The installer detects your OS and architecture automatically. On macOS it supports both Intel and Apple Silicon. On Linux it supports x64 and arm64. The binary is installed to `~/.feynman/bin` and added to your `PATH`.
 
-```bash
-feynman --version
-```
-
-## Windows PowerShell
+On **Windows**, open PowerShell as Administrator and run:
 
 ```powershell
 irm https://feynman.is/install.ps1 | iex
 ```
 
-## npm fallback
+This installs the native Windows binary and adds Feynman to your user `PATH`. You can re-run either installer at any time to update to the latest version.
 
-If you already manage Node yourself:
+## npm / npx
+
+If you already have Node.js 18+ installed, you can install Feynman globally via npm:
 
 ```bash
 npm install -g @companion-ai/feynman
 ```
 
-## Local Development
+Or run it directly without installing:
 
-For contributing or local development:
+```bash
+npx @companion-ai/feynman
+```
+
+The npm distribution bundles the same core runtime as the native installer but depends on Node.js being present on your system. The native installer is preferred because it ships a self-contained binary with faster startup.
+
+## Post-install setup
+
+After installation, run the guided setup wizard to configure your model provider and API keys:
+
+```bash
+feynman setup
+```
+
+This walks you through selecting a default model, authenticating with your provider, and optionally installing extra packages for features like web search and document preview. See the [Setup guide](/docs/getting-started/setup) for a detailed walkthrough.
+
+## Verifying the installation
+
+Confirm Feynman is installed and accessible:
+
+```bash
+feynman --version
+```
+
+If you see a version number, you are ready to go. Run `feynman doctor` at any time to diagnose configuration issues, missing dependencies, or authentication problems.
+
+## Local development
+
+For contributing or running Feynman from source:
 
 ```bash
 git clone https://github.com/getcompanion-ai/feynman.git