add documentation

docs-site/docs/installation.md

@@ -0,0 +1,36 @@
+# Installation
+
+!!! warning "Two different things"
+**A)** Building this **documentation site** (MkDocs) — instructions below.  
+ **B)** Installing **Claude Code** the product — use Anthropic’s official installers only.
+
+## Install Claude Code (official product)
+
+Follow the [Claude Code overview](https://code.claude.com/docs/en/overview): native install script, Homebrew, WinGet, VS Code extension, JetBrains plugin, desktop app, or web. This recovered repository **does not** ship a supported way to compile or install the product from source.
+
+## Build this documentation site (local)
+
+Requires Python 3.10+.
+
+```bash
+cd docs-site
+python3 -m venv .venv
+source .venv/bin/activate   # Windows: .venv\Scripts\activate
+pip install -r requirements.txt
+mkdocs serve
+```
+
+Open `http://127.0.0.1:8000` to preview.
+
+## Publish (GitHub Pages)
+
+On push to `main`, the workflow `.github/workflows/pages.yml` builds the site and pushes to the `gh-pages` branch (also runs when `README.md` or the workflow file changes).
+
+1. In the GitHub repo: **Settings → Pages → Build and deployment → Branch `gh-pages` / `/ (root)`**.
+2. After the first deploy, set `site_url` in `docs-site/mkdocs.yml` to your real Pages URL (e.g. `https://<user>.github.io/<repo>/`) so canonical links and search work correctly. Also update `repo_url` if your fork uses a different owner or name.
+
+The deploy step sets **`enable_jekyll: false`** so GitHub Pages serves static files correctly (adds `.nojekyll`).
+
+## Advanced setup (official)
+
+For system requirements, updates, and uninstallation of the **product**, see [Advanced setup](https://code.claude.com/docs/en/setup) in the official docs.