Docs: add top-level index, refactor according to diataxis

docs/site/getting-started/index.md

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+# Getting Started
+
+Create your own clan with these initial steps and manage a fleet of machines with one single testable git repository!
+
+### Prerequisites
+
+=== "**Linux**"
+
+    Clan depends on nix installed on your system. Run the following command to install nix.
+
+    ```bash
+    curl --proto '=https' --tlsv1.2 -sSf -L https://install.determinate.systems/nix | sh -s -- install
+    ```
+
+    If you already have installed Nix, make sure you have the `nix-command` and `flakes` configuration enabled in your ~/.config/nix/nix.conf.
+    The determinate installer already comes with this configuration by default.
+
+    ```bash
+    # /etc/nix/nix.conf or ~/.config/nix/nix.conf
+    experimental-features = nix-command flakes
+    ```
+
+=== "**NixOS**"
+
+    If you run NixOS the `nix` binary is already installed.
+
+    You will also need to enable the `flakes` and `nix-commands` experimental features in your configuration.nix:
+
+    ```nix
+    { nix.settings.experimental-features = [ "nix-command" "flakes" ]; }
+    ```
+
+=== "**Other**"
+
+    Clan doesn't offer dedicated support for other operating systems yet.
+
+### Step 1: Add Clan CLI to Your Shell
+
+Add the Clan CLI into your development workflow:
+
+```bash
+nix shell git+https://git.clan.lol/clan/clan-core#clan-cli
+```
+
+You can find reference documentation for the `clan` cli program [here](../reference/cli/index.md).
+
+Alternatively you can check out the help pages directly:
+```terminalSession
+clan --help
+```
+
+### Step 2: Initialize Your Project
+
+Set the foundation of your Clan project by initializing it as follows:
+
+```bash
+clan flakes create my-clan
+```
+
+This command creates the `flake.nix` and `.clan-flake` files for your project.
+It will also generate files from a default template, to help show general clan usage patterns.
+
+### Step 3: Verify the Project Structure
+
+Ensure that all project files exist by running:
+
+```bash
+cd my-clan
+tree
+```
+
+This should yield the following:
+
+``` { .console .no-copy }
+.
+├── flake.nix
+├── machines
+│   ├── jon
+│   │   ├── configuration.nix
+│   │   └── hardware-configuration.nix
+│   └── sara
+│       ├── configuration.nix
+│       └── hardware-configuration.nix
+└── modules
+    └── shared.nix
+
+5 directories, 9 files
+```
+
+```bash
+clan machines list
+```
+
+``` { .console .no-copy }
+jon
+sara
+```
+
+!!! success
+
+    You just successfully bootstrapped your first clan directory.
+
+---
+
+### What's Next?
+
+- [**Installer**](./installer.md): Setting up new computers remotely is easy with an USB stick.
+
+---