doc: the quickstart is not one - 'Getting to know CuOS'

It builds, boots, then spends six sections updating, patching, rolling back and
factory-resetting. That is a guided tour, and its own lead already said so:
'this page is for looking inside afterwards'. The name promised the opposite,
and it collided with cuos-release's Quickstart, which really is three commands.

Also removed: '(Variant 2 or 3 style)', a leftover of the deleted variants.

Author: simonwalz

README.md

@@ -39,7 +39,7 @@ and VMs, one machine or a fleet.
 | build a bootable system — disk image, ISO installer or LXC container | [cuos-release](https://github.com/cuos-dev/cuos-release#readme) |
 | deploy and manage services on one | [cuos-iac](https://github.com/cuos-dev/cuos-iac#readme) |
 | build your own OS or init app on CuOS | [Development Guide](docs/development-guide.md) |
-| see the pieces working end to end | [Quickstart](docs/quickstart.md) |
+| build one and take it apart, to learn how it works | [Getting to know CuOS](docs/getting-to-know-cuos.md) |
 
 The name is the description: **C**ontainer **U**pdate **OS** — built from a
 container, updates itself, and is a whole operating system rather than a runtime

docs/quickstart.md docs/getting-to-know-cuos.mddocs/quickstart.md renamed to docs/getting-to-know-cuos.md

@@ -1,15 +1,16 @@
-# CuOS Quickstart
+# Getting to know CuOS
 
-A minimal end-to-end walkthrough to build, boot and update a CuOS based system.
+Build one, boot it, then take it apart: update it, patch it, break it, roll it
+back. By the end you will have used every mechanism CuOS has, on a machine you
+can throw away.
 
-> Audience: Engineers who want to try CuOS quickly (Variant 2 or 3 style) without reading all reference docs first.
->
-> Prerequisites: Linux/macOS build host, Docker, `jq`, ~6 GB free disk space, a VM platform (QEMU/VirtualBox/Proxmox) or spare USB device.
+> Prerequisites: Linux/macOS build host, Docker, `jq`, ~6 GB free disk space, a VM platform (QEMU/VirtualBox/Proxmox) or spare USB device. Allow an hour.
 
-> **If you only want a running system**, you do not need this repository. Clone
+> **This is not the fast way to a running system.** For that you do not need
+> this repository at all: clone
 > [cuos-release](https://github.com/cuos-dev/cuos-release), write a
-> `system.json` and run `./cuos-release/tool.sh image` — its README walks you
-> through it. This page is for looking inside afterwards.
+> `system.json`, run `./cuos-release/tool.sh image` — its README is three
+> commands long. Come back here when you want to know what you just built.
 
 ---