Start the desktop after install by enabling the login screen and services

docs/install.md

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+# Install
+
+`./install.sh` takes a machine with nothing but Arch on it to a running Blob
+desktop. Every step is idempotent, reports what it did, and can be previewed
+with `--check`.
+
+## Layout
+
+| Path | Role |
+| --- | --- |
+| `install.sh` | flags and the order the steps run in |
+| `install/helpers/lib.sh` | reporting, file copies, unit queries |
+| `install/helpers/as-root.sh` | `as_root`, a no-op when already root |
+| `install/steps/directories.sh` | the directories the shell and scripts expect |
+| `install/steps/packages.sh` | repo and AUR packages, and the yay bootstrap |
+| `install/steps/config.sh` | the `BLOB_PATH` symlink and everything under `~/.config` |
+| `install/steps/services.sh` | system services, systemd drop-ins, user units |
+| `install/steps/login.sh` | SDDM, the session entry, and the first launch |
+
+## Steps
+
+1. **`BLOB_PATH`** is symlinked to the checkout at `~/.local/share/blob`. Nothing
+   under `bin/`, `shell/`, `themes/` or `default/` is ever copied.
+2. **Directories** are created, including `~/.config/systemd/user/app.slice.d`
+   and `~/wallpapers`.
+3. **Packages** come from `packages/blob.packages` and
+   `packages/blob-aur.packages`. A machine with no AUR helper gets `yay-bin`
+   built once with `makepkg`. See [packages.md](packages.md).
+4. **Config** is copied into `~/.config`: `hypr/`, the themed app configs,
+   `blob/shell.json`, the uwsm environment, and the icon font.
+5. **User units** land in `~/.config/systemd/user` and are enabled, not started:
+   they are all `WantedBy=graphical-session.target`, so they come up with the
+   session. `blob-speaker-tuning.service` is left out, because
+   `blob-audio-tuning` installs it only on machines with a tuning profile.
+6. **systemd drop-ins** are written under `/etc`: the shutdown timeouts, the
+   oomd pressure thresholds, the plocate prune paths, and the sleep hooks.
+7. **System services** are enabled: NetworkManager, resolved, bluetooth, cups,
+   avahi, docker, power-profiles-daemon, and oomd.
+   `NetworkManager-wait-online.service` is masked so a slow DHCP lease cannot
+   hold up the login screen.
+8. **The login screen** is SDDM. Three pieces have to be in place:
+
+   | File | Why |
+   | --- | --- |
+   | `/usr/local/share/wayland-sessions/blob.desktop` | the session SDDM offers |
+   | `/etc/sddm.conf.d/10-blob.conf` | Wayland greeter, run on Hyprland, remember the last session |
+   | `/etc/sddm/hyprland-greeter.lua` | the greeter's own tiny Hyprland config |
+
+   The greeter config matters more than it looks: SDDM's stock Wayland greeter
+   runs on `weston`, which Blob does not install, so a default SDDM would fail
+   to draw anything. `sddm.service` is enabled and the default systemd target is
+   set to `graphical.target`, which an Arch install without a display manager
+   does not have.
+9. **Launch.** When the installer was run from a console and nothing graphical
+   is running, it starts `sddm.service` so the desktop appears without a reboot.
+   `--no-launch` prints the command instead. `--autologin` writes
+   `/etc/sddm.conf.d/99-blob-autologin.conf` for the current user.
+
+## Flags
+
+| Flag | Effect |
+| --- | --- |
+| `--check` | report every change, write nothing, exit 1 if anything differs |
+| `--force` | overwrite files that differ from the repo copy |
+| `--skip-packages` | directories, config and services only |
+| `--autologin` | skip the SDDM prompt for this user |
+| `--no-launch` | leave the login screen for the next reboot |
+
+## Uninstall
+
+`./uninstall.sh` removes the config, the user units, the `/etc` drop-ins, the
+session entry and the symlink, restoring any `.bak` the installer left.
+`--keep-session` keeps the session entry and the SDDM config, `--keep-state`
+keeps `~/.local/state/blob`. `sddm.service` is left enabled either way, so the
+machine still reaches a login screen.