Document the app, and specifically how the post-reboot check works

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

README.md

@@ -1,17 +1,90 @@
-# layer_wizard
+# Layer Wizard
 
-A new Flutter project.
+A GUI installer wizard for permanently layering an RPM package onto a
+bootc/image-based (read-only root) Linux system via `rpm-ostree install`,
+with a guided reboot step and a one-click rollback if the result looks wrong.
 
-## Getting Started
+Built for Universal Blue / Fedora bootc systems, where plain `dnf install`
+refuses to run (the root filesystem is read-only) and the persistent
+mechanism is `rpm-ostree install <pkg>`, which stages a new deployment that
+only takes effect after a reboot.
 
-This project is a starting point for a Flutter application.
+## What it does
 
-A few resources to get you started if this is your first Flutter project:
+1. **Welcome** — shows the currently booted version/image.
+2. **Package** — enter a package name; "Check" confirms it resolves
+   (`dnf repoquery`) before anything privileged happens.
+3. **Confirm** — review the package and what's about to happen.
+4. **Apply** — runs `pkexec rpm-ostree install -y <package>`, with the
+   PolicyKit password prompt and a live streamed log. On success, offers
+   **Reboot Now** / **Reboot Later**.
+5. After rebooting, the app **launches itself automatically** and asks:
+   "Is everything working correctly?" — **Yes, keep this update**, or
+   **No, something's wrong — roll back**, which runs
+   `pkexec bootc rollback --apply` (reboots immediately into the previous
+   deployment).
 
-- [Learn Flutter](https://docs.flutter.dev/get-started/learn-flutter)
-- [Write your first Flutter app](https://docs.flutter.dev/get-started/codelab)
-- [Flutter learning resources](https://docs.flutter.dev/reference/learning-resources)
+## How the post-reboot check works
 
-For help getting started with Flutter development, view the
-[online documentation](https://docs.flutter.dev/), which offers tutorials,
-samples, guidance on mobile development, and a full API reference.
+This system has no `greenboot` and no automated bad-boot detection
+(`systemd-bless-boot.service` exists but isn't wired up to anything here) —
+so the rollback offer is **self-reported**, not automatic. Two pieces make
+that work:
+
+- **Autostart entry.** Right after a successful install,
+  `ConfirmationMarker.installAutostart()` (`lib/confirmation_marker.dart`)
+  writes `~/.config/autostart/com.ironmagma.layer_wizard.desktop`, with
+  `Exec=` pointing at the currently-running binary
+  (`Platform.resolvedExecutable`). KDE's session runs everything in
+  `~/.config/autostart/` on login, which is what makes the app reappear on
+  its own right after the reboot — you don't have to remember to open it.
+
+- **The check itself runs on every launch, not just via autostart.**
+  `lib/main.dart`'s `_StartupRouter` calls `ConfirmationMarker.read()` before
+  deciding what to show:
+
+  ```dart
+  future: ConfirmationMarker.read(),
+  builder: (context, snapshot) {
+    final pending = snapshot.data;
+    if (pending != null) return ConfirmationPage(pending: pending);
+    return const WizardHomePage();
+  }
+  ```
+
+  `read()` just checks whether
+  `~/.local/state/layer_wizard/pending_confirmation.json` exists and parses
+  it. That file is written by the wizard right after a successful install
+  (`ConfirmationMarker.write(...)` in `lib/wizard_page.dart`), and deleted —
+  along with the autostart entry — as soon as you click **Keep** or
+  **Roll back** in `lib/confirmation_page.dart`.
+
+  Running the check unconditionally at startup (rather than only when
+  launched via autostart) is deliberate: if autostart doesn't fire for some
+  reason, or you dismiss it and reopen the app later, you still land on the
+  confirmation screen instead of that pending state getting silently
+  dropped.
+
+## Project layout
+
+- `lib/ostree_service.dart` — all privileged/unprivileged shelling out:
+  `rpm-ostree status --json`, `dnf repoquery`, `pkexec rpm-ostree install`,
+  `pkexec bootc rollback --apply`, `pkexec systemctl reboot`.
+- `lib/confirmation_marker.dart` — the pending-confirmation marker file and
+  autostart `.desktop` entry (write/read/clear, install/remove).
+- `lib/wizard_page.dart` — the install wizard (`Stepper`-based).
+- `lib/confirmation_page.dart` — the post-reboot "did this work?" screen.
+- `lib/main.dart` — startup routing between the two.
+
+Privilege escalation follows the same pattern as the sibling
+[`dnf-package-store`](https://github.com/quine-global-labs/dnf-package-store)
+app: `pkexec` through the desktop PolicyKit agent, with stdout/stderr
+streamed line-by-line into the UI.
+
+## Building
+
+```
+flutter build linux
+```
+
+Produces `build/linux/x64/release/bundle/layer_wizard`.