docs: publish docs/ to the GitHub wiki and reorganise the user guide

- scripts/publish-wiki.sh publishes every page listed in SECTIONS, copies
  images, writes a sectioned sidebar and footer, and removes stale pages.
  --check fails on links to missing files or headings and on docs pages
  that are neither published nor excluded.
- New wiki.yml runs the check on pull requests and pushes to main, and
  publishes when release.yml calls it or when started by hand.
- Split USER_GUIDE.md into topic pages (files, synced folders, photos,
  sharing, computers, launcher and tray); add Getting started and FAQ.
- Make the COPR repository the main Fedora path, with update and
  uninstall steps for every package type.
- Fix the stale CAPTCHA note in CLI.md, document pdfs unlock and lock,
  and drop the broken AGENTS.md link from CONTRIBUTING.md.

docs/GETTING_STARTED.md

@@ -0,0 +1,72 @@
+# Getting started
+
+From installing to your first synced folder in a few minutes.
+
+> [!IMPORTANT]
+> Proton Drive for Linux is an unofficial client, built by the community and not by Proton. Try it
+> first with files you also have somewhere else.
+
+## 1. Install
+
+| Distribution | Command |
+|---|---|
+| Fedora 44 or newer | `sudo dnf copr enable narl-rs/proton-drive-linux`<br>`sudo dnf install proton-drive-linux` |
+| Arch Linux | `paru -S proton-drive-for-linux` (or any other AUR helper) |
+| Debian, Ubuntu 24.04 or newer | Download the `.deb` from the [latest release](https://github.com/narrrl/proton-drive-linux/releases/latest), then `sudo apt install ./proton-drive-linux_*_amd64.deb` |
+| NixOS | See [Installation → NixOS](INSTALL.md#nixos-flake) |
+
+On GNOME, also install the
+[AppIndicator extension](https://extensions.gnome.org/extension/615/appindicator-support/) to see
+the tray icon. [Installation](INSTALL.md) has every option, building from source, and the optional
+extras.
+
+## 2. Sign in
+
+![The sign-in window](../images/login.png)
+
+1. Open **Proton Drive** from your applications menu.
+2. Sign in with your Proton email and password, and the two-factor code if your account has one.
+   If Proton asks you to prove you are human (common on a VPN), solve the challenge in the window
+   that opens.
+3. Wait a moment. Your Proton Drive appears as the folder `~/ProtonDrive`.
+
+The app starts the Proton Drive service for you, and the service starts by itself whenever you
+log in. Your session is kept in the system keyring (GNOME Keyring, KWallet or KeePassXC), so you
+sign in only once.
+
+## 3. Choose how files are kept
+
+There are three ways to have your files on this computer. You can mix them freely.
+
+| | Takes disk space | Works offline | Use it for |
+|---|---|---|---|
+| **Online only** (the default in `~/ProtonDrive`) | Only for files you opened recently | Only files still in the cache | Most of your Drive: archives, media, anything large |
+| **Available offline** | Yes | Yes | Files and folders you need on the road |
+| **Synced folder** | Yes, a full copy | Yes | Folders that live on this computer, such as `~/Documents`, backed up to Proton Drive |
+
+- **Online only:** open `~/ProtonDrive` in your file manager. Files download when you open them.
+- **Available offline:** select a file or folder in the app and turn on **Available offline**.
+  [More about offline files](FILES.md#keep-files-available-offline).
+- **Synced folder:** in the app, open **Computers** and choose **Add Folder to Sync**.
+  [More about synced folders](SYNCED_FOLDERS.md).
+
+## 4. Know where to look
+
+- **Tray icon:** shows whether everything is up to date, and pauses or resumes sync.
+- **Sync → Overview** in the app: what is uploading, what is waiting, and anything that needs you.
+- **Search launcher:** bind `pdfs-prompt` to a keyboard shortcut to find any file in Proton Drive
+  or your home folder. See [Search launcher and tray](LAUNCHER_AND_TRAY.md).
+
+> [!WARNING]
+> `~/ProtonDrive` is your Proton Drive, not a copy. Deleting a file there moves it to the Proton
+> Drive Trash on every device. You can restore it from **Trash** in the app.
+
+## Next steps
+
+- [User guide](USER_GUIDE.md): everything the app, tray and launcher do.
+- [FAQ](FAQ.md): short answers to common questions.
+- [Troubleshooting](TROUBLESHOOTING.md): when something does not work.
+- [Recovering on a new computer](RECOVERY.md): read this before you rely on the client for
+  backups.
+- Prefer a terminal? `pdfs status` shows the state of everything, and the
+  [command-line reference](CLI.md) lists every command.