docs: unify markdown files with documentation titles

This is preparational work to reduce the surface are of the different mappings

We want to reduce the following:

/guides/secrets.md -> Guides/getting started/How to use flakes with sops -> with '# Secrets Management'

- Title
- URI
- Filepath

should follow a stricter pattern to make it easy to maintain

docs/site/guides/getting-started/configure-disk.md

@@ -0,0 +1,74 @@
+By default clan uses [disko](https://github.com/nix-community/disko) which allows for declarative disk partitioning.
+
+To see what disk templates are available run:
+```{.shellSession hl_lines="10" .no-copy}
+$ clan templates list
+
+Available 'clan' template
+├── <builtin>
+│   ├── default: Initialize a new clan flake
+│   ├── flake-parts: Flake-parts
+│   └── minimal: for clans managed via (G)UI
+Available 'disko' templates
+├── <builtin>
+│   └── single-disk: A simple ext4 disk with a single partition
+Available 'machine' templates
+├── <builtin>
+│   ├── demo-template: Demo machine for the CLAN project
+│   ├── flash-installer: Initialize a new flash-installer machine
+│   ├── new-machine: Initialize a new machine
+│   └── test-morph-template: Morph a machine
+```
+
+
+For this guide we will select the `single-disk` template, that uses `A simple ext4 disk with a single partition`.
+
+!!! tip
+    For advanced partitioning, see [Disko templates](https://github.com/nix-community/disko-templates) or [Disko examples](https://github.com/nix-community/disko/tree/master/example).
+    You can also [contribute a disk template to clan core](https://docs.clan.lol/guides/disko-templates/community/)
+
+
+To setup a disk schema for a machine run
+
+```bash
+clan templates apply disk single-disk jon --set mainDisk ""
+```
+
+Which should fail and give the valid options for the specific hardware:
+
+```shellSession
+Invalid value  for placeholder mainDisk - Valid options:
+/dev/disk/by-id/nvme-WD_PC_SN740_SDDQNQD-512G-1201_232557804368
+```
+
+Re-run the command with the correct disk:
+
+```bash
+clan templates apply disk single-disk jon --set mainDisk "/dev/disk/by-id/nvme-WD_PC_SN740_SDDQNQD-512G-1201_232557804368"
+```
+
+Should now be successful
+
+```shellSession
+Applied disk template 'single-disk' to machine 'jon'
+```
+
+A disko.nix file should be created in `machines/jon`
+You can have a look and customize it if needed.
+
+!!! Danger
+    Don't change the `disko.nix` after the machine is installed for the first time, unless you really know what you are doing.
+    Changing disko configuration requires wiping and reinstalling the machine.
+
+## Deploy the machine
+
+**Finally deployment time!**
+
+This command is destructive and will format your disk and install NixOS on it! It is equivalent to appending `--phases kexec,disko,install,reboot`.
+
+
+```bash
+clan machines install [MACHINE] --target-host root@<IP>
+```
+
+