Ask Dev Updater for the checkout, not for the app inside it

Dev Updater's unit is a project -- a directory in a checkout -- that
produces components, so this declaration belongs at the repository root
where it can say where each half lives. `cwd` is how a component says
that, and it is what the old file was working around: sitting in `app/`,
it reached the backend with `../server/Cargo.toml` and `../server/service`,
which described the layout backwards.

So the file says what this repository produces: the backend, built and
serviced in `server/`, and then the APK, built in `app/`. The order is
unchanged and still the point -- a failing APK build leaves the phone the
APK it already had rather than half of a matched pair.

The service script gains dev-updater's note about lingering. A user
service stops at logout unless `loginctl enable-linger` is set, which for
this one matters more than for a build server: the phone reaches ai-server
whether or not anyone is logged in at the desk.

**This changes the project path, so the phone's existing entry (at
~/repos/ai-app/app) has to be removed and the checkout root added
instead**, and its components accepted once.

Verified against dev-updater's current parser rather than by reading its
schema: the declaration loads, `cargo build --release` resolves into
server/, app/build-apk.sh into app/, the service script to an absolute
path, and APK discovery from the root still finds the built APK.
`./server/service status` prints not-installed and exits 0.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017xn8nHw1tw1R6PtiY1eEtw

server/service

@@ -3,6 +3,12 @@
 # drive from the phone -- and for you to drive by hand, which is the same
 # thing.
 #
+# Declared as the Server component of this checkout in `.dev-updater.ron`
+# at the repository root, so the card drives it like any other project's.
+# One button is worth knowing about before pressing it: on a phone that
+# reaches ai-server through the tunnel rather than through Dev Updater,
+# Stop leaves this server down until someone starts it again here.
+#
 #   ./service install | uninstall | start | stop | restart | status
 #
 # `status` prints exactly one of `running`, `stopped` or `not-installed`
@@ -16,7 +22,10 @@
 # with a message telling you to run it yourself once instead.
 #
 # User services on purpose: a system unit needs root to install, and a
-# build machine's own account is where a dev server belongs.
+# build machine's own account is where a dev server belongs. Note that a
+# user service stops at logout unless lingering is enabled
+# (`loginctl enable-linger $USER`), which you want for this one: the phone
+# reaches this server whether or not anyone is logged in at the desk.
 set -eu
 
 SCRIPT_DIR=$(cd "$(dirname "$0")" && pwd)